Photovoltaic cell for laser beam power detection

Abstract

SOLUTION: In a wireless optical power transmission system comprising a transmitter and a receiver, the transmitter comprises: a laser emitting a beam; a scanning mirror for steering the beam toward the receiver; and a control unit receiving signals from a detection unit on the receiver and controlling the beam power and the scanning mirror. The receiver has a photovoltaic cell 71 having a bandgap energy of 0.75-1.2 eV, and the photovoltaic cell is provided with a plurality of conductors 72 on a receiving surface of beams 79a - 79g. A cover layer 78 of a material blocking illumination of wavelengths outside that of the laser, is disposed on the photovoltaic cell. The cover layer has anti-reflective coatings on its top and bottom surfaces.EFFECT: The detection unit generates a signal representing the power of the laser beam impinging upon the receiver, independent of illuminations other than that of the laser beam. The control unit thus can maintain the laser power impinging on the receiver.SELECTED DRAWING: Figure 7A

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic cells, and more particularly to a photovoltaic cell adapted to convert a beam from a laser power source into electrical energy in a wireless power system.

Background Art

[0002] Photovoltaic cells, known as PV cells, are designed and used in many systems to convert light (visible or invisible) into electrical energy. In a wireless power supply system, a photovoltaic cell is used to convert laser light directed from a transmitter to the cell into useable electricity. In such a system, accurately measuring the amount of laser light received by the cell is important for many reasons, such as maintaining the correct aim of the beam, maintaining the safe operation of the system, and efficiently converting the power generated by the photovoltaic cell into stable useable power.

[0003] In a typical photovoltaic cell, light is converted into electrical energy using one or more pn junctions and extracted from the cell using two electrodes. The bottom electrode is usually metal-coated, and typically there are two options for the top electrode. (i) A metal grid typically made of aluminum, silver, or gold. This metal grid has low series resistance but reflects some of the light hitting the grid itself, preventing its incidence on the cell. (ii) A continuous, substantially transparent conductive coating such as indium tin oxide (ITO). This conductive coating transmits most of the light incident on the cell but has high resistance losses because it has higher resistance than a metal grid structure. ​​

[0004] According to the metal grid, due to reflection from the metal grid, there is typically a trade-off between resistive loss and optical loss. The resistive loss is measured by V / R. Here, V is the voltage of the cell and R is the series resistance. This resistive loss decreases as the metal coverage ratio of the cell increases, while the optical loss increases as the metal coverage ratio of the cell increases, as is known as the "shading effect". Typically, there is an optimal balance between these two factors. This balance typically depends on the predicted cell illumination and current of a photovoltaic (PV) cell. 2 / R . Here, V is the voltage of the cell and R is the series resistance. This resistive loss decreases as the metal coverage ratio of the cell increases, while the optical loss increases as the metal coverage ratio of the cell increases, as is known as the "shading effect". Typically, there is an optimal balance between these two factors. This balance typically depends on the predicted cell illumination and current of a photovoltaic (PV) cell. It is known that as the metal coverage ratio of the cell increases, while the optical loss increases as the metal coverage ratio of the cell increases, as is known as the "shading effect". Typically, there is an optimal balance between these two factors. This balance typically depends on the predicted cell illumination and current of a photovoltaic (PV) cell. It is known that as the metal coverage ratio of the cell increases, while the optical loss increases as the metal coverage ratio of the cell increases, as is known as the "shading effect". Typically, there is an optimal balance between these two factors. This balance typically depends on the predicted cell illumination and current of a photovoltaic (PV) cell. hotovoltaic (PV)) cell. It is known that as the metal coverage ratio of the cell increases, while the optical loss increases as the metal coverage ratio of the cell increases, as is known as the "shading effect". Typically, there is an optimal balance between these two factors. This balance typically depends on the predicted cell illumination and current of a photovoltaic (PV) cell.

[0005] Non-Patent Document 1 describes that a PV cell achieving a conversion efficiency of 44.5% from sunlight to electricity has been developed. It is described that a PV cell achieving a conversion efficiency of 44.5% from sunlight to electricity has been developed.

[0006] According to Green et al. (Non-Patent Document 2), as published in Non-Patent Document 3 presented at the 29th PV Solar Energy Conference and Exhibition held in Amsterdam, the Netherlands in September 2014, the reported highest PV efficiency was 46%. It was presented at the 29th PV Solar Energy Conference and Exhibition held in Amsterdam, the Netherlands in September 2014, and as published in Non-Patent Document 3, the reported highest PV efficiency was 46%. It was presented at the 29th PV Solar Energy Conference and Exhibition held in Amsterdam, the Netherlands in September 2014, and as published in Non-Patent Document 3, the reported highest PV efficiency was 46%.

[0007] Non-Patent Document 4 proposes a composite glass "lenslet" designed to minimize grid loss by concentrating light away from the conductor grid. Such a composite lenslet pattern requires an exact placement with respect to the metal grid and is not widely used. Non-Patent Document 4 proposes a composite glass "lenslet" designed to minimize grid loss by concentrating light away from the conductor grid. Such a composite lenslet pattern requires an exact placement with respect to the metal grid and is not widely used. Non-Patent Document 4 proposes a composite glass "lenslet" designed to minimize grid loss by concentrating light away from the conductor grid. Such a composite lenslet pattern requires an exact placement with respect to the metal grid and is not widely used. It requires an exact placement with respect to the metal grid and is not widely used.

[0008] Unless such a composite "lenslet" optical system is used, there are resistive losses and shading losses Since there is a normal trade-off between loss and gain, typically the optical loss results in the range of 2% to 10%, and the same resistance loss occurs for high-concentration cells. The same resistance loss occurs for high-concentration cells.

[0009] In a review by Non-Patent Document 5 covering currently available PV optical systems, without using a composite structure optical system that requires an exact arrangement for metal grids, if the trade-off between the conductor ratio and optical shading is eliminated, it is stated that a 3% to 20% improvement in cell efficiency would be possible in a photovoltaic cell. without using a composite structure optical system that requires an exact arrangement for metal grids, if the trade-off between the conductor ratio and optical shading is eliminated, it is stated that a 3% to 20% improvement in cell efficiency would be possible in a photovoltaic cell. if the trade-off between the conductor ratio and optical shading is eliminated, it is stated that a 3% to 20% improvement in cell efficiency would be possible in a photovoltaic cell. it is stated that a 3% to 20% improvement in cell efficiency would be possible in a photovoltaic cell.

[0010] Non-Patent Document 6 describes a system that minimizes shading loss. Instead of typically flat rectangular-shaped conductors, the use of rounded finger-shaped conductors is proposed. Instead of typically flat rectangular-shaped conductors, the use of rounded finger-shaped conductors is proposed. Due to the finger shape, much of the incident light reflected from the PV element surface is returned to and absorbed by the PV element surface. Due to the finger shape, much of the incident light reflected from the PV element surface is returned to and absorbed by the PV element surface.

[0011] To optimize prior art PV cell conductors, an optimization screen is used by PV designers. An example of such a grid computer is shown below. To optimize prior art PV cell conductors, an optimization screen is used by PV designers. An example of such a grid computer is shown below. https: / / www2.pvlighthouse.com.au / calculators / Grid%20calculator / Grid%20calculator .aspx

[0012] When using such a grid computer, the user can select different shapes (rectangular, triangular, elliptical, pseudo-rectangular) of conductive fingers, as well as different materials, widths, and heights. However, since the user cannot select an optical cover layer, such a coating cannot be optimized. By using this tool to optimize the grid, it becomes possible to compare different trade-offs between the metal cover ratios of different cells. The same website has shading since the user cannot select an optical cover layer, such a coating cannot be optimized. By using this tool to optimize the grid, it becomes possible to compare different trade-offs between the metal cover ratios of different cells. The same website has shading between the metal cover ratios of different cells. The same website has shading Define the shading loss as "the shading loss is caused by the presence of metal on the upper surface of the solar cell that prevents light from entering the solar cell." The shading loss is determined by the transparency of the upper surface. This transparency is defined as the ratio of the upper surface covered by metal with respect to a flat upper surface. The transparency is determined by the width of the metal lines on the surface and the spacing between the metal lines. An important practical limit is the minimum line width associated with a particular metallization technology. For the same transparency, a technology with a narrow line width can make the finger spacing denser, thus reducing the emitter resistance loss. The current common approach to optimizing the conductor grid can also be learned from Non-Patent Document 7. Page 62 of the online reference states that "the optimal width (Wb) of the bus bar occurs when the resistance loss of the bus bar is equal to its shadowing loss," and different well-known methods in the industry for reducing such losses are shown. Different options for increasing light trapping within the cell are described, but no option for recycling the reflected light is mentioned. However, while the PV cells described in such references provide high efficiency, these PV cells are generally optimized for maximum efficiency when converting solar energy into electrical energy. This may have different technical requirements from converting the power of a laser beam into electrical energy. Therefore, a wireless system that overcomes at least some of the drawbacks of the prior art systems and methods

[0013]

[0014]

[0015] ​​​​​​​​​​​​​​A photovoltaic cell for converting a transmitted laser beam into electric power is required.

[0016] The disclosures of each publication referred to in this section and other sections of this specification are hereby incorporated by reference in their entireties. Each is incorporated herein by reference.

Prior Art Documents

Non-Patent Documents

[0017]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

[0018] The present disclosure describes a novel exemplary system for use within a wireless laser power transmission system that includes a PV cell having a cover layer that is used when converting the power of a laser beam into electrical energy. The configurations described in the present disclosure simultaneously achieve several of the following objectives to improve the photovoltaic efficiency, improve safety, and these PVs by achieving the following objectives simultaneously: improvement of the photovoltaic efficiency, improvement of safety, and these PVs Seek the accuracy of power measurements performed using cells. a) Reduction of the dependency between the metal finger coverage rate and shading. b) Reduction of the amount of reflected light from the cell. c) Reuse of the reflected light into electrical energy. d) Reduction of the resistive losses in the series resistance of the conductor. e) Improvement of the accuracy of laser power measurement using a photovoltaic cell when illuminated from different angles. Improvement. f) Improvement of the accuracy of laser power measurement using a photovoltaic cell when used under different lighting conditions such as outdoors, indoors, or near a heat source. Improvement. g) Confirmation that the directed transmitted laser power reaches the intended receiver at the intended power level. That is, confirmation that no unreasonable level of power "strays" into the path. That is, confirmation that no unreasonable level of power "strays" into the path. Confirmation.

[0019] In many cases, the beam aiming mechanism of a wireless laser power transmission system and / or the safety mechanism of the system rely on an accurate measurement of the laser power received by the photovoltaic cell. For example, if the laser aiming is adjusted until the maximum power from the PV is generated, accurate aiming can be impaired by sunlight that can bias the measurement at a fraction of time, such as when the cell is illuminated at one moment but not the next. In a system where safety depends on power measurement, illumination from different directions should be optimized to give similar power measurement results, and sunlight or a heat source should not bias the measurement results beyond a small safety margin. The devices of the present disclosure allow for being essentially independent of the measurement from the illumination direction and other light sources of different wavelengths that can illuminate the system. For example, if the laser aiming is adjusted until the maximum power from the PV is generated, accurate aiming can be impaired by sunlight that can bias the measurement at a fraction of time, such as when the cell is illuminated at one moment but not the next. In a system where safety depends on power measurement, illumination from different directions should be optimized to give similar power measurement results, and sunlight or a heat source should not bias the measurement results beyond a small safety margin. In a system where safety depends on power measurement, illumination from different directions should be optimized to give similar power measurement results, and sunlight or a heat source should not bias the measurement results beyond a small safety margin. In a system where safety depends on power measurement, illumination from different directions should be optimized to give similar power measurement results, and sunlight or a heat source should not bias the measurement results beyond a small safety margin. In a system where safety depends on power measurement, illumination from different directions should be optimized to give similar power measurement results, and sunlight or a heat source should not bias the measurement results beyond a small safety margin. In a system where safety depends on power measurement, illumination from different directions should be optimized to give similar power measurement results, and sunlight or a heat source should not bias the measurement results beyond a small safety margin. The devices of the present disclosure allow for being essentially independent of the measurement from the illumination direction and other light sources of different wavelengths that can illuminate the system.

[0020] The light reflected by the photovoltaic cell is collected from both the front surface and the conductor and is then projected onto the metal grid. When directed towards cell areas not covered by the metal grid, it increases the coverage of the metal grid. This reduces the resistance loss and at the same time reduces the shading effect. , a positive correlation based on the generated power in a manner independent of the beam direction and even of the beam uniformity. This allows accurate optical power estimation. If the system illuminates only a portion of the cell, the narrow conductor will be larger than in the case of uniform illumination. This results in large resistive losses, making optical power estimates based on electrical power or current inaccurate. The described configurations can have low resistive losses, making it possible to estimate optical power based on power measurements. Become accurate.

[0021] However, light is applied to the photovoltaic cells from different directions and the grid A complex pattern that may include several orders of Bragg reflection is typically caused by the periodic structure of the This effect causes a number of problems. First, the efficiency is reduced due to the loss of reflected light. Second, reflected light is a safety hazard. Third, the amount of reflected light varies depending on the lighting direction. Since it depends on the photovoltaic cell, optical power measurement is inaccurate and may be inaccurate for safety and aiming purposes. In many cases, the safety mechanisms of the system are such that the photovoltaic cells The measurement depends on accurate measurement of the laser power.

[0022] Does not include PV reorientation when beam direction is changed, i.e. PVs automatically adjust to maximize power In a typical wireless power system, where the laser is not tilted randomly, the laser can be steered in almost any direction. Such systems typically require a directional illumination of the cell from the direction of the cell surface. It operates from the line up to 60 degrees. As a result, the light reflected from the conductor is reflected at different angles , spreads from the normal of the cell by about ±70 degrees or more, and the main reflection is at an angle opposite to the incoming beam . A symmetrical field of view is maintained so that the beam can enter from either side of the PV. In this case, all collection systems located inside the field of view must be transparent (including the support structure of the optical elements), otherwise, it will interfere with the cell's ability to collect light from those directions .

[0023] An efficient collection system must also, in order to be efficient, cover various parts in various directions within this field of view. So, when the beam is incident from one direction and generates a reflected beam in another direction, in order for the collection system to capture and collect the reflected beam in that other direction on the way, since the collection system is opaque, inevitably, it must block the incident light coming from that other direction . In other words, expressed in terms of the points of the provided field of view, all the incident angles included in the field of view generate reflections in some direction. When recycling the light (or reflected light) going in this direction, it is necessary to effectively exclude this direction from the field of view by arranging an opaque collection system in the direction of the reflection .

[0024] .

[0024] The object of the present invention is to introduce such a system and improve the efficiency, aiming accuracy and safety of the system .

[0025] In one exemplary implementation, the shapes of a plurality of conductors in the PV are selected such that the conductors reflect light in a wide pattern . A typical structure mainly depends on the manufacturing ability and the predicted field of view of the incident light, that is, the angles at which light can enter. However, as a general concept, a common ​​ A flat surface, square, or rectangular conductor grid is not preferred, while round and triangular grids are advantageous.

[0026] This system can use PVs having a plurality of conductors shaped optimally to prevent shading losses. The shape of the plurality of conductors in the PV can be selected such that they reflect light in a broad pattern. For example, the plurality of conductors may be in a rounded finger shape or a triangular shape. Thereby, the reflected light from the conductors is directed towards the absorbing PV cells or is completely internally reflected by a cover layer covering the cells, improving the efficiency of the system. Thereby, furthermore, dangerous reflected light that could damage the eyes is prevented from being reflected from the PV cells. This is because the light reflected from the conductors is diffused and is not reflected in a uniform manner.

[0027] The PV configuration of the present disclosure is significantly different from prior art PVs in that the cover layer can be coated with antireflection (AR) coatings on both of its interface surfaces, i.e., an outer AR coating between the cover layer and the outside air and an inner AR coating between the cover layer and the light absorption surface of the PV cell material.

[0028] The outer antireflection (AR) coating is essentially adapted to transmit only infrared light at the wavelength of a typical laser beam and reflect all other wavelengths that collide, i.e., wavelengths that are likely to be present in external illumination and that can affect the ability to measure the laser wavelength of the PV cell. That is, the AR coating is, for example, wavelengths such as The cell does not need to reflect the insensitive wavelength. This is because it does not affect the measurement at the laser wavelength. This is because

[0029] In addition, the cover layer should include a material that absorbs wavelengths other than the wavelength of the beam. As a result, any wavelength not reflected by the AR coating is absorbed by the cover layer and does not reach the pn junction of the PV cell, so there is no inaccurate reading of the amount of laser power transmittance. Therefore, the upper layer of the PV cell should also be absorptive for visible wavelengths that can be incident on the upper layer of the semiconductor PV cell material itself because they were not reflected by the AR coating, similar to the cover layer itself. This is achieved by selecting an upper layer of the PV cell material with a sufficiently low bandgap. As a result, any wavelength not reflected by the AR coating is absorbed by the cover layer and does not reach the pn junction of the PV cell, so there is no inaccurate reading of the amount of laser power transmittance. Thus, there is no inaccurate reading of the amount of laser power transmittance. Therefore, the upper layer of the PV cell should also be absorptive for visible wavelengths that can be incident on the upper layer of the semiconductor PV cell material itself because they were not reflected by the AR coating, similar to the cover layer itself. This is achieved by selecting an upper layer of the PV cell material with a sufficiently low bandgap. This is achieved by selecting an upper layer of the PV cell material with a sufficiently low bandgap. This is achieved by selecting an upper layer of the PV cell material with a sufficiently low bandgap. This is achieved by selecting an upper layer of the PV cell material with a sufficiently low bandgap.

[0030] One purpose of blocking wavelengths other than the wavelength of the laser beam from reaching the pn junction of the PV absorption cell is that when the receiver is acting as a safety power meter for the transmitter, this receiver needs to give an accurate reading of the amount of colliding laser beams. That is, other incident illumination should not interfere with this measurement and should be blocked before hitting the absorption PV cell. One purpose of blocking wavelengths other than the wavelength of the laser beam from reaching the pn junction of the PV absorption cell is that when the receiver is acting as a safety power meter for the transmitter, this receiver needs to give an accurate reading of the amount of colliding laser beams. That is, other incident illumination should not interfere with this measurement and should be blocked before hitting the absorption PV cell. That is, other incident illumination should not interfere with this measurement and should be blocked before hitting the absorption PV cell.

[0031] Furthermore, the cover layer needs to have a high refractive index. This is to lower the critical angle of total internal reflection (TIR) and capture as much of the laser beam incident on the cover layer and reflected from the surface and conductor as possible. This effect will be explained in detail below. This is for the purpose of maximizing the amount of illumination reaching the absorption PV cell. The laser beam reflected from the conductor Furthermore, the cover layer needs to have a high refractive index. This is to lower the critical angle of total internal reflection (TIR) and capture as much of the laser beam incident on the cover layer and reflected from the surface and conductor as possible. This is to lower the critical angle of total internal reflection (TIR) and capture as much of the laser beam incident on the cover layer and reflected from the surface and conductor as possible. This effect will be explained in detail below. This is for the purpose of maximizing the amount of illumination reaching the absorption PV cell. This is for the purpose of maximizing the amount of illumination reaching the absorption PV cell. The laser beam reflected from the conductor By a part of the beam being retroreflected from the cover layer, leakage from the PV cell that would have occurred in the absence of the cover layer can be prevented. This is because.

[0032] This also has the advantage that any light emerging from the PV cell, after multiple reflections inside the cover layer between the PV cell surface and the conductor, and total internal reflection from above the cover layer, will be in different "random" directions and positions. This is in contrast to prior art PV configurations that reflect the beam in a uniform manner.

[0033] The upper part of the absorption PV layer at the bottom of the cover layer may also be covered by an AR coating that maximizes the absorption of the light impinging from the cover layer into the PV cell material.

[0034] According to a further implementation example, and making use of the advantages provided by the double - reflection - preventing coated cover layer, a wireless optical power transmission system including a transmitter, a receiver, and a control unit is described. Here, a) The transmitter includes a laser adapted to emit a beam and a scan mirror adapted to steer the beam towards the receiver. b) The receiver includes a photovoltaic cell having at least one junction with a band - gap energy of 0.75 eV to 1.2 eV and a detection unit adapted to detect the power of the laser beam impinging on the receiver independently of illumination at wavelengths outside the range of the wavelength of the laser beam. c) The control unit is adapted to receive a signal from the detection unit and to interact with at least one of (i) the power of the beam emitted by the laser and (ii) the position of the scan mirror.

[0035] The detection unit then generates a signal representative of the power of the laser beam impinging on the receiver. This signal is advantageously independent of illumination of wavelengths outside that of the laser beam.

[0036] The control unit can then use this signal to operate in two functionally separate ways. In one implementation, the control unit can use this signal to: (i) determine the position of the beam; and (ii) the position of a “scanning” mirror, This allows the system to be adjusted to give the optimum aiming power to the receiver. The system is actively tailored to provide optimal power input at the ultimate target, the receiver. This is the traditional role of a control system, which acts to regulate or "adjust" the

[0037] The term "scan mirror" is used herein to refer to any movable mirror. The term refers to the use of fixed-position mirrors or charged It includes a mirror that moves slowly to aim the beam at the receiver and maintains that aim. This is intended as an alternative description of "scanning" mirrors, which have different functions.

[0038] According to a second configuration, the control system may determine whether the laser power beam is capable of causing damage. Act as a safety verification system to ensure that the aircraft is not deflected in an unexpected direction. This system involves a laser beam directing a beam of a given power to a receiver. However, the receiver does not receive all or part of that power, and the beam power Alerts about conditions that indicate at least some of the information is being biased in an unintended direction. This is the opposite of the role that a control system normally plays, i.e., controlling the system. Rather, it is achieved by using a control system for the purpose of verifying the system state. In this mode, the control system inputs data from the laser regarding the output power that the laser is instructed to give or is actually giving as measured at the transmitter, and inputs data from the scan mirror regarding the direction in which the beam is aimed. These data are then combined in the controller and compared with the signal generated in the detector unit regarding the actual laser power received there. A deviation greater than a predetermined error or loss margin between the laser powers predicted from these two sets of data can be used to trigger a safety warning state regarding the forward beam transmission or regarding reducing or deflecting the beam in the presence of an obstacle in the beam path.

[0039] Cover layer

[0040] The cover layer can be advantageously applied on a conductor, and this cover layer typically has a high refractive index greater than 1.5, preferably greater than 1.6 or 1.65, or has a semiconductor coating layer with a refractive index greater than 2, but surely has a refractive index greater than 1.3.

[0041] In one implementation example, the cover layer consists of a polymer layer or a dielectric layer covered by a glass layer. The cover layer is an optical layer with a uniform composition, but typically has an upper volume and a lower volume and may consist of many different transparent or translucent layers and has the following characteristics.

[0042] The upper volume of the optical cover layer is typically in contact with the ambient environment which is typically air, but other materials It may be in contact with the material. The upper volume is often more protective than the soft inner volume of the cover layer and is a hard glass layer. Additionally, the upper volume can be selected to have a higher refractive index than the main volume to increase the probability that internal light undergoes total internal reflection. The lower part of the optical cover layer contacts both the PV surface (typically including an AR coating) and the conductor described above. The cover layer needs to be as transparent as possible for the incoming beam wavelength, requires an optical density of less than 2 for the beam wavelength, and an optical density of less than 1 or less than 0.5 is preferred. Some materials may tolerate an optical density of less than 0.1 or less than 0.01, but nevertheless, the cover layer needs to be configured to block, absorb, or reflect most other wavelengths except the beam wavelength. This prevents other wavelengths that may enter from sunlight or other illumination sources from reaching the pn junction. Thus, it needs to have an optical density of at least 0.5 for these wavelengths. The upper part of the PV is usually covered by an AR coating. The AR coating is typically adapted to minimize reflection between air (refractive index of about 1) and PV (typically a refractive index of 2 - 4) in prior art PVs. For the cells of the present disclosure, the lower AR coating needs to be designed to minimize reflection of the laser wavelength between the PV (refractive index 2 - 4) and the optical cover layer (refractive index 1.5 - 2) for the beam wavelength, but at the same time, it also needs to reflect wavelengths shorter and longer than this away from the cell. Both AR coatings can be used to remove unwanted wavelengths. The upper part of the cover layer is for the beam between air (refractive index of about 1) and the upper part of the cover layer

[0043] In the case of the cells of the present disclosure, the lower AR coating needs to be designed to minimize reflection of the laser wavelength between the PV (refractive index 2 - 4) and the optical cover layer (refractive index 1.5 - 2) for the beam wavelength, but at the same time, it also needs to reflect wavelengths shorter and longer than this away from the cell. Both AR coatings can be used to remove unwanted wavelengths. The upper part of the cover layer is for the beam between air (refractive index of about 1) and the upper part of the cover layer and the upper part of the cover layer ​The AR coating is adapted to minimize reflection of some wavelengths while increasing reflection of other wavelengths. The insulating layer may be covered by a coating.

[0044] The cover layer "shields" the PN junction from light that is not the laser beam itself. This is important for the safety and accuracy of the aiming measurement. This can be achieved by directing the light toward the PV cell or by reflecting it away from the PV cell. As mentioned above, the AR coating on the cover layer reflects external illumination outside the laser band, The cover layer absorbs what is not reflected. In many cases, PN junctions are very long-wavelength. Since the optical fiber is inefficient for long wavelengths, there is no need to block such wavelengths.

[0045] The overall structure of the grid itself

[0046] The density of the grid lines must be selected depending on various parameters, as explained below. There is.

[0047] The spacing between the grid lines is greater than the operating wavelength divided by twice the refractive index of the cover layer This is advantageous in some cases. d>λ / 2n where d is the spacing between the conductor lines, λ is the operating wavelength in vacuum, and n is the refractive index of the cover layer.

[0048] It is also advantageous if the spacing between the grid lines is smaller than 100 times the operating wavelength in vacuum. It becomes. d<100λ

[0049] Also, the optical cover layer should be designed to absorb short wavelengths even if it has minimal absorption at the operating wavelength. It is also preferable that the ion exchange rate is selected as follows.

[0050] If the conductor is coated with a diffusion coating, the above dimensional constraints can be relaxed.

[0051] Physical explanation

[0052] When light is reflected from the grid of a prior art photovoltaic cell, the light is reflected at an unknown angle and is usually irrecoverable. The construction of a light collection system that will not interfere with the incoming beam is difficult if not impossible. At the same time, when a prior art photovoltaic cell is placed under direct sunlight 100 mW / cm of sunlight is converted into power, and the reading of the laser power becomes 2 inaccurate, which can affect safety and aiming operations.

[0053] The photovoltaic cells of the present disclosure utilize four distinct design features that overcome many of the above drawbacks of prior art PV cells. 1. The incoming beam strikes the conductor in a reduced field of view due to the high refractive index of the cover layer used. According to Snell's law, the beam angle is reduced by sin(θ1)=n1 / n2×sin(θ2), so that light reflected at an angle greater than the maximum field of view in the cover layer can be operated to be reflected towards the cell without blocking the field of view. 2. The grid structure serves to increase the amount of light reflected outside the field of view of the incoming beam, both due to its dense grid lines and the structure of each conductor. 3. The cover layer serves as a collection and reflection system. This is because most of the beam undergoes total internal reflection by the cover layer and is reflected back towards the photovoltaic cell. 4. Since sunlight is absorbed / reflected by the cover layer and its associated AR coating, it does not affect the power measurement value.

[0054] The use of the cover layer and the features described above can reduce the optical loss of the laser beam. The ability to reuse a portion of the light allows for a reduction in resistive losses due to an increase in the covered area of the conductor, an increase in the fill factor of the cell, and an increase in the maximum power point voltage and current, thus enabling further improvement of the device. To facilitate efficient reflection to the photovoltaic cell, the thickness of the cover layer should be less than the width of the photovoltaic cell. If it is thick, light will escape from the side surfaces of the cover layer.

[0055] All of the above design features enable the construction of a grid with much "shading" compared to the normal shading described in the prior art. The shape of a single conductor line needs to be selected to maximize higher-order reflections from the grid, which is typically as described above.

[0056] The upper volume should have an AR coating for air or for predicted ambient materials such as water or vacuum.

[0057]

[0058]

[0059]

[0060] Advantages when illuminating the cell with an infrared laser

[0060] The features described herein are particularly useful for photovoltaic cells designed to convert infrared laser light into electrical energy. This is due to several advantages provided by such cells.

[0061] First, such cells are typically illuminated by a power that is 10 to 100 times greater per unit area compared to the one-sun conditions to which conventional solar cells are typically exposed. CPV cells ​Compared with [the comparison object], this design has a wide field of view and intentionally reduces the efficiency with respect to sunlight.

[0062] Second, infrared lasers rely on low-energy photons, which generate low voltage and high current in a pn junction that requires a low bandgap compared to an optimized cell and need a low bandgap. Since the current is high, the resistive losses become significant.

[0063] The pn junction in such a cell is tuned by selecting a material with a sufficiently low bandgap to "ignore" long-wavelength photons that are longer than the wavelength of the laser beam. As a result, in a situation where a receiver is placed near a heat source such as a heating element or an incandescent lamp, output parameters such as power, current, and voltage are much less susceptible to the influence of long-wavelength infrared photons.

[0064] Third, unlike the typically uniform sunlight radiation across the entire area of the cell, laser radiation forms a concentrated spot and tends to "underfill" the cell. The laser beam generally has an approximately circular, elliptical, or rectangular shape with a Gaussian or higher-order Gaussian decay power curve in many cases. The non-uniform power curve complicates the optimization of the conductor thickness, and what the ski

[0065] Fourth, the specular reflection from the cell of a high-power laser can pose safety concerns. Either blocking or diffusing is required. In any case, the reflection from the cell of the present disclosure is of low power, significantly reducing safety concerns. The reflection from the cell of the present disclosure is of low power, significantly reducing safety concerns.

[0066] Advantages of illuminating a cell using a wireless power beam emission system

[0067] When a current cell is used as a component of a wireless power system, it has many advantages. Typically, such a system can power a portable electronic device equipped with a battery having a capacity of 1 to 100 watts-hour. Typically, the required charging power is on the order of 0.5 to 10 W, which requires a charging beam of 1 to 30 W to be used.

[0068] The typical diameter of the beam is several mm, and the smaller the beam, the more difficult it becomes to continue focusing in the range of 1 to 10 m. Therefore, the non-diffusing reflection of 2 to 10% of the beam involves a significant risk (20 mW to 1 W). Therefore, it is essential to reduce the total amount of light reflected by the conductor and at the same time diffuse the light. Reducing the reflection from the cell is also essential. This cell typically gives a reflection of up to 1%, instead of the usual 2 to 10%. .

[0069] Therefore, according to an exemplary implementation of the device described in the present disclosure, a power conversion device is provided that converts optical power into power suitable for optical wireless power transmission using a laser beam. This power conversion device is (i) a photovoltaic cell having a plurality of conductors on a surface adapted to receive a laser beam, the photovoltaic cell having at least one junction having a bandgap energy of 0.75 eV to 1.2 eV, and a photovoltaic cell having a junction; (ii) The cover layer disposed on the photovoltaic cell and includes, and the cover layer restricts the transmission of illumination having wavelengths outside the wavelength range of the laser beam by either absorption or reflection to transmit the laser beam to the photovoltaic cell and includes a material adapted to do so, the laser beam has a wavelength in the range of 700 nm to 1500 nm, the wavelength of the illumination outside the wavelength range of the laser beam is in the range of 550 nm to 700 nm , the transmittance of the cover layer for the wavelength of the laser beam is at least 50% higher than the transmittance of the cover layer for wavelengths in the range of 550 nm to 700 nm, and the power conversion device has a conversion efficiency of power at the wavelength of the laser beam that is at least 2.5 times higher than the conversion efficiency of power at a wavelength of 550 nm. In such a power conversion device, the bandgap energy can be tuned to the wavelength of the laser so that the conversion efficiency of the optical power to electrical power for any wavelength that is at least 25% longer than the wavelength of the laser is more than 4 times smaller than the conversion efficiency at the laser wavelength. In any of the devices described above, the cover layer further includes

[0070] either (i) a first anti-reflection coating disposed on the surface of the cover layer away from the photovoltaic cell, which reflects illumination having wavelengths outside the wavelength range of the laser beam and is adapted to transmit the laser beam to the cover layer, or (ii) a second anti-reflection coating disposed between the surface of the photovoltaic cell and the cover layer, which reflects illumination having wavelengths outside the wavelength range of the laser beam and transmits the laser beam to the cover layer. In any of the devices described above, the cover layer further includes (i) a first anti-reflection coating disposed on the surface of the cover layer away from the photovoltaic cell, which reflects illumination having wavelengths outside the wavelength range of the laser beam and is adapted to transmit the laser beam to the cover layer, or (ii) a second anti-reflection coating disposed between the surface of the photovoltaic cell and the cover layer, which reflects illumination having wavelengths outside the wavelength range of the laser beam and is adapted to transmit the laser beam to the cover layer. The first anti-reflection coating reflects illumination having wavelengths outside the wavelength range of the laser beam and transmits the laser beam to the cover layer, or (ii) a second anti-reflection coating disposed between the surface of the photovoltaic cell and the cover layer, which reflects illumination having wavelengths outside the wavelength range of the laser beam and transmits the laser beam to the cover layer, and reflects illumination having wavelengths outside the wavelength range of the laser beam and transmits the laser beam At least one of the second anti-reflection coatings adapted to transmit to the photovoltaic cell may be included.

[0071] Still further implementations described in the present disclosure relate to a safety system for a wireless optical power transmission system including a transmitter, a receiver, and a control unit. Here, (i) The transmitter includes a laser adapted to emit a beam, and a scan mirror adapted to steer the beam to the receiver and (ii) The receiver is a photovoltaic cell having a plurality of conductors on a surface adapted to receive a laser beam, having at least one junction having a bandgap energy of 0.75 eV to 1.2 eV and includes a cover layer disposed on the photovoltaic cell wherein the cover layer limits illumination having wavelengths outside the range of the wavelength of the laser beam by either absorption or reflection and transmits the laser beam to the photovoltaic cell and includes a material adapted to do so, (iii) The control unit receives first data representing the position of the scan mirror, receives second data representing the power of the beam emitted by the laser from the transmitter, determines the predicted power incident on the photovoltaic cell from the first data and the second data, and compares the predicted power with the power of the laser beam impinging on the receiver measured by the photovoltaic cell and is adapted to indicate a safety issue that may occur if the predicted power deviates from the measured power by a predetermined level above.

[0072] According to still other embodiments of the present application, a wireless optical power transmission system including a transmitter and a receiver is provided is obtained, the transmitter includes a laser adapted to emit a beam, a scanning mirror adapted to steer the beam to a receiver, and a control unit adapted to receive a signal from a detection unit in the receiver and control at least one of (i) the power of the beam emitted by the laser and (ii) the position of the scanning mirror, and the receiver includes a photovoltaic cell having a plurality of conductors on a surface adapted to receive the laser beam, the photovoltaic cell having at least one junction having a bandgap energy of 0.75 eV to 1.2 eV, the photovoltaic cell being adapted to detect the power of the laser beam reaching the photovoltaic cell, the receiver includes a cover layer disposed on the photovoltaic cell and adapted to absorb or reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the photovoltaic cell, and the receiver includes at least one of (i) a first antireflection coating disposed on a surface of the cover layer away from the photovoltaic cell and adapted to reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the cover layer, or (ii) a second antireflection coating disposed between the surface of the photovoltaic cell and the cover layer and adapted to reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the photovoltaic cell, and the receiver includes a cover layer including a material adapted to absorb or reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the photovoltaic cell, (i) a first antireflection coating disposed on a surface of the cover layer away from the photovoltaic cell and adapted to reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the cover layer, or (ii) a second antireflection coating disposed between the surface of the photovoltaic cell and the cover layer and adapted to reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the photovoltaic cell, and (ii) a second antireflection coating disposed between the surface of the photovoltaic cell and the cover layer and adapted to reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the photovoltaic cell, or a second antireflection coating disposed between the surface of the photovoltaic cell and the cover layer and adapted to reflect illumination having a wavelength outside the range of the wavelength of the laser beam and transmit the laser beam to the photovoltaic cell, and at least one of them, and When the detection unit is independent of other illumination other than the wavelength of the laser beam, it is directed to the receiver A signal representing the power of the laser beam that collides is generated, and the control unit is directed to the receiver To maintain the power of the collision, it is adapted to control at least one of (i) the beam and (ii) the position of the scan mirror is adapted to control at least one of.

[0073] The optical power adapted for optical wireless power transmission using the laser beam described in this disclosure To convert into power, a further power conversion device is A power conversion device having at least one junction having a bandgap energy of 0.75 eV to 1.2 eV A power conversion device having an external layer through which laser light is transmitted to the one junction The external layer may include a power conversion device having. The external layer is relative to the normal of the surface of the external layer When illuminated from any direction between ±20° with respect to the normal of the surface of the external layer, at least 80 % efficiency is configured to transmit at least the first wavelength to the one junction, where , (i) The conversion efficiency of the power conversion device is at least 30%, and the first wavelength is 7 00 nm to 1500 nm near-infrared wavelength, and (ii) The external layer of the power conversion device is configured to reflect or absorb a portion of the incident illumination of the second wavelength of 550 nm to 700 nm, so that less than 60% of the illumination of the second wavelength Reaches the at least one junction when illuminated through the external layer from any direction between ±20° with respect to the normal of the surface of the external layer, and the conversion efficiency of the power conversion device for the second wavelength is less than 20%, and (iii) The external layer of the power conversion device is at least the first of 300 nm to 550 nm When illuminated from any direction between ±20° with respect to the normal of the surface of the external layer, at least 80% of the illumination of the first wavelength is transmitted to the one junction, where (i) The conversion efficiency of the power conversion device is at least 30%, and the first wavelength is 700 nm to 1500 nm near-infrared wavelength, and (ii) The external layer of the power conversion device is configured to reflect or absorb a portion of the incident illumination of the second wavelength of 550 nm to 700 nm, so that less than 60% of the illumination of the second wavelength configured to absorb or reflect three wavelengths such that, as a result, when irradiated through the outer layer from any direction within ± 20° with respect to the normal of the surface of the outer layer, at least 50% of the power of the third wavelength is absorbed before reaching the at least one joint and the conversion efficiency of the power conversion device for the third wavelength is less than 10%, and (iv) the conversion efficiency of the power conversion device for a fourth wavelength between 1500 nm and 2000 nm is less than 5%, and is at least one of

[0074] As described in the present disclosure, other embodiments of a power conversion device that converts an optical power beam into electrical power include (i) a semiconductor device having a pn junction adapted to absorb the optical power beam and (ii) an upper conductor and a lower conductor in electrical contact with the semiconductor device, the upper conductor covering a portion of the upper surface of the semiconductor device, and (iii) an optical layer disposed on the upper surface of the semiconductor device, the optical layer including an upper volume and a lower volume, the lower volume being in optical contact with the upper surface of the semiconductor device and in optical contact with the upper conductor of the semiconductor device, and the upper volume being in optical contact with air and (a) the upper conductor is adapted to reflect at least 30% of the light impinging on the upper conductor and (b) the optical layer has an optical density of less than 2 with respect to the optical power beam and (c) the upper conductor is adapted to direct at least 25% of the light reflected by the upper conductor at an angle greater than (1 / refractive index of the lower volume). and (c) the upper conductor is adapted to direct at least 25% of the light reflected by the upper conductor at an angle greater than n -1 (1 / refractive index of the lower volume).

[0075] In such a power conversion device, at least a part of the light reflected by the conductor may be reflected at an angle to undergo total internal reflection from the upper surface of the upper volume. The upper volume of the optical layer itself may be adapted to reduce the reflection of an optical power beam incident from a medium with a refractive index approximately equal to 1 as an antireflection coating. The upper volume of the optical layer may further be a scratch-resistant coating. In the case of the antireflection coating, it may be further adapted to reduce the reflection of the optical power beam over an angle of at least -10 degrees to +10 degrees with respect to the normal to the upper surface .

[0076] In addition, in any of the power conversion devices described above, the coverage ratio of the upper surface covered by the upper conductor may be at least 4%. The conductor itself may be made of metal and may contain at least partially aluminum, gold, silver, or copper .

[0077] Furthermore, in the power conversion device described above, the geometric protrusion area of the part of the conductor aligned at an angle of at least sin -1 (1 / refractive index of the lower volume) with respect to the upper surface of the semiconductor device should be at least 25% of the area of the semiconductor device multiplied by the coverage ratio of the upper surface covered by the upper conductor .

[0078] According to yet another implementation of such a power conversion device, user reflection from the power conversion device can be diffused. In such a case, the diffuse reflection from the power conversion device may have a viewing angle of at least 1.5 milliradians. Furthermore, measured in m units 2 ​​​Multiply the area of the resulting semiconductor device by the cube of the design maximum power of the cell measured in watts, and then multiply the result by the bandgap of the junction measured in square joules to obtain P which is less than 214×10 3 ×(bandgap) 2 A as shown -30 such as 214×10 -30 and less than become

[0079] In any of the power conversion devices described above, the upper conductor may include a conductive grid having a finger-shaped or triangular shaped contour

[0080] Finally, according to yet another implementation described in the present disclosure, there is provided a power conversion device that converts optical power into electrical power suitable for optical wireless transmission using a laser beam. This power conversion device includes a photovoltaic cell having a plurality of conductors on a surface adapted to receive the laser beam, the photovoltaic cell having at least one junction having a bandgap energy of 0.75 eV to 1.2 eV and a cover layer disposed on the junction, where the cover layer performs at least one of absorption or reflection of illumination having a wavelength in the range of 550 nm to 700 nm and is adapted to transmit the laser beam toward the photovoltaic cell. The laser beam has a wavelength in the range of 700 nm to 1500 nm and the transmittance of the cover layer for the wavelength of the laser beam is at least 50% higher than the transmittance of the cover layer for wavelengths in the range of 550 nm to 700 nm and the power conversion device has a conversion efficiency to power at the wavelength of the laser beam that is at least 2.5 times greater than the conversion efficiency to power at a wavelength of 55 0 nm The cover layer includes a material adapted to transmit the laser beam toward the photovoltaic cell, and the laser beam has a wavelength in the range of 700 nm to 1500 nm The transmittance of the cover layer for the wavelength of the laser beam is at least 50% higher than the transmittance of the cover layer for wavelengths in the range of 550 nm to 700 nm and the power conversion device has a conversion efficiency to power at the wavelength of the laser beam that is at least 2.5 times greater than the conversion efficiency to power at a wavelength of 55 0 nm The conversion efficiency of the power conversion device to power at the wavelength of the laser beam is at least 2.5 times greater than the conversion efficiency to power at a wavelength of 55

Brief Description of the Drawings

[0081] The present invention will be more fully understood and appreciated from the following detailed description when used in conjunction with the drawings. It will be understood.

[0082]

Figure 1

Figure 2

Figure 3

Figures 4A - 4C

Figure 5

Figures 6A - 6B

Figure 7A

Figure 7B

Figures 7C - 7D

Figures 8A - 8B

Figure 8C

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0083] Here, refer to FIG. 1 which schematically shows a typical structure of a photovoltaic cell. The photovoltaic cell is made from a p -type semiconductor 13 attached to an n-type semiconductor 11 or in some cases in contact with the n-type semiconductor 11 but still separated by other layers to form a pn junction 12. A complete metal contact is arranged on the back of the cell 14, and a partial metal contact in the form of a grid (or similar structure) 15 is arranged on the front of the cell. This allows light to penetrate the space between the conductors. The incident illumination generates a current 16 through the load. Here, referring to FIG. 2, the first two orders of Bragg reflection of an incident beam 23 in a prior art rectangular grid photovoltaic cell 21 are schematically shown. The incoming beam 23 that collides with the metal grid 22 of the photovoltaic cell 21 reflects approximately 2 - 10% of the power in the beam 21 by the conductor grid 22 in the Bragg pattern. This includes several orders such as the zero order 24 and the first order 25 shown in FIG. 2. Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is

[0084] Here, referring to FIG. 2, the first two orders of Bragg reflection of an incident beam 23 in a prior art rectangular grid photovoltaic cell 21 are schematically shown. The incoming beam 23 that collides with the metal grid 22 of the photovoltaic cell 21 reflects approximately 2 - 10% of the power in the beam 21 by the conductor grid 22 in the Bragg pattern. This includes several orders such as the zero order 24 and the first order 25 shown in FIG. 2. Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is

[0085] Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is Here, referring to FIG. 3, such a typical multiple reflection 31 from the surface 32 of a prior art photovoltaic cell is shown. Reflections of at least 20 orders are visible. The power at each "order" depends very strongly on the angle of illumination, causing safety and aiming problems. Total reflection is Over an angle of about 5 degrees from the zero-order reflection, the zero-order reflection is the strongest reflection. The higher the order of the reflection, the smaller the power contained compared to the case of a lower order. This is particularly different from the cell of the present invention where reflection to higher-order modes exceeding the critical angle of the optical cover layer is preferred. Here, reference is made to FIGS. 4A, 4B, and 4C. Alternative grid contours used in PV cells are schematically shown. FIG. 4A shows the reflection from a grid of rectangular conductors. This reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold.

[0086] Here, reference is made to FIGS. 4A, 4B, and 4C. Alternative grid contours used in PV cells are schematically shown. FIG. 4A shows the reflection from a grid of rectangular conductors. This reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern. Here, reference is made to FIGS. 4A, 4B, and 4C. Alternative grid contours used in PV cells are schematically shown. FIG. 4A shows the reflection from a grid of rectangular conductors. This reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern. The reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern. The reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern. Here, reference is made to FIGS. 4A, 4B, and 4C. Alternative grid contours used in PV cells are schematically shown. FIG. 4A shows the reflection from a grid of rectangular conductors. This reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern. Here, reference is made to FIGS. 4A, 4B, and 4C. Alternative grid contours used in PV cells are schematically shown. FIG. 4A shows the reflection from a grid of rectangular conductors. This reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern. Here, reference is made to FIGS. 4A, 4B, and 4C. Alternative grid contours used in PV cells are schematically shown. FIG. 4A shows the reflection from a grid of rectangular conductors. This reflection is generated at an angle opposite to the incident beam angle. FIG. 4B shows the reflectivity from a triangular reflector. This triangular reflector divides the beam into two wide-angle beams and functions well in a small field of view (FOV). FIG. 4C shows the reflection from a rounded conductor that spreads over a wide angle. A preferred implementation (not shown in FIGS. 4A - 4C) is a conductor covered by a diffusive upper layer, which can spread the radiation in a very wide pattern.

[0087] The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. The structures shown in FIGS. 4B and 4C, as well as the diffusive coating on the conductor, enhance the higher-order reflections from the grid, thus enhancing the "reuse" of the reflected light. It should be understood that it is generally not possible to manufacture a perfect geometric shape, and such illustrations serve as simple examples. It is preferred to select a pattern that spreads light over a wide FOV, such as a diffusive, circular, or triangular shape. A shape like a triangle with a reflector tilt greater than the threshold angle, which reflects a significant percentage of the light at a wide angle, is preferred. The conductor is typically made of a reflective material such as a metal that reflects at least 30% of the incident light. Typically, a material that reflects at least 90% of the light, such as aluminum, silver, or gold. A material is selected. The conductor may be covered by a diffusive coating.

[0088] Referring now to FIG. 5, terms used in the present disclosure are explained. The angle of the reflected light dependency is shown as a function of the incident light on the finger-shaped conductor in PV51 having a back electrode and a pn junction in addition to the conductor 52. The angle 55 is the local angle formed by the intersection of the line 57 tangent to the surface of the finger conductor at the point 56 on the conductor and the normal 58. The area projected onto the upper surface 59 of the PV by the conductor 52 is shown below the PV and is numbered 53. The area projected onto the PV surface by a part of the conductor 52 where the angle is less than the threshold value is shown below the PV and is numbered 54.

[0089] Referring now to FIGS. 6A and 6B, as proposed in the present application, the difference between the incoming beam angle 61a of a known PV cell 62 without a high refractive index cover layer and the incoming beam angle 61b of a cell 64 having a high refractive index cover layer 63 is shown. Each is illuminated by either the beam 61a in FIG. 6A or the beam 61b in FIG. 6B. The beam 6 1b passes through a cover layer 63 which is a transparent coating layer and is referred to as an optical cover layer. The upper part of the optical cover layer 63 may be a anti-reflection coating that reduces the reflection of the beam 61b, and most of the reflection is allowed to enter the optical cover layer 63. The lower surface 65 of the optical cover layer 63 is in contact with both the upper part of the pn junction of the cell 64 and the conductor (not shown) of the cell 64. There is an anti-reflection coating between the lower part 65 of the optical cover layer 63 and the cell 64 . This is when crossing from the refractive index of the lower part 65 of the optical cover layer 63 to the upper part of the cell 64 is adapted to reduce reflection of the light beam 61b. The optical cover layer 63 typically has a high refractive index and an optical density that allows at least 80% of the power to pass through, preferably having an optical density of less than 2 when measured with respect to the optical beam 61b. Due to the high refractive index of the coating layer 63, the light beam 61b reaches the upper surface of the cell 64 at an incident angle smaller than the angle at which the beam 61a parallel to 61b enters the cell 62. The thickness of the coating layer 63 should be less than the width of the cell 64.

[0090] Referring now to FIG. 7A, a photovoltaic cell 71 similar to that shown above in FIG. 5 with a cover layer 78 added is shown. This figure shows the different paths that the incident beam can take when it collides with the PV structure. Beams 79a, 79b, 79c, and 79g are shown to be absorbed by the cell 71 when present in a known PV cell having the same conductive carrier rate. On the other hand, beam 79d is shown to be reflected by the side of the conductor 72 and immediately absorbed by the cell 71. Beam 79e is shown to be reflected by the upper part of the conductor 72 and leak out of the device in a manner similar to what occurs when it collides with a prior art rectangular conductor. That is, the reflection is lost and not converted into electrical energy. Beam 7 9f is shown to be reflected from the conductor at an angle such that the beam is lost in a prior art PV cell. However, since the current PV is covered by the cover layer 78, beam 79f collides with the inside of the upper surface of the cover layer 78 at an incident angle greater than the critical angle with respect to the upper surface boundary and is thus reflected back towards the PV surface as beam 79f'. However, since the current PV is covered by the cover layer 78, beam 79f collides with the inside of the upper surface of the cover layer 78 at an incident angle greater than the critical angle with respect to the upper surface boundary and is thus reflected back towards the PV surface as beam 79f'. Rather than being lost, even after additional reflections such as those typically shown in FIG. 7A, the cell absorbs it. The optical conductor 72 is wider than similar conductors in prior art cells so that it has lower resistance and higher reflectivity compared to prior art conductors. The shape of the optical conductor 72 is designed to maximize the projected area of the portion of the conductor that is tilted at an angle greater than 80% of the critical angle calculated based on the refractive index below the optical cover layer 78 Reflections at such angles ultimately reach the cell again, increasing the probability that the cell will absorb it and convert it to power . The conductor 72 typically has a reflectivity of greater than 80 to 90%, but may in some cases have a lower reflectivity. The conductor 72 may be made of a metal such as aluminum, silver, gold, molybdenum, copper, nickel, or tungsten, and may be coated with a diffusive coating such as an opal coating . Alternatively, the conductor may have small reflective structures or particles deposited thereon. The plurality of conductors 72 are spaced such that reflections from the assembly are maximized to a degree greater than 80% of the critical angle calculated based on the refractive index below the optical cover layer 78 . Such spacing typically exceeds 0.5 wavelengths / refractive index and is less than 100 wavelengths . Although the conductors in FIGS. 7A and 5 above and FIGS. 7B and 8C that follow are shown as finger-shaped , it should also be understood that these conductors may also have any other suitable profile, such as the triangular shape of FIG. 4B, that provides multiple internal reflections of the beam within the cover layer 78 .

[0091] Referring now to FIG. 7B, which shows the PV cell of FIG. 7A according to the present disclosure, above the cover layer 78

[0092] ​​​​​Anti-reflection coatings 73 and 74 are applied to the front and bottom surfaces.

[0093] Referring now to FIG. 7C, the prominence of the viewing angle of the apparent light source is shown. This is the angle subtended by the apparent light source when viewed from a point within the space Specifically, the resolution of the human eye is such that a typical retinal photoreceptor views the surrounding environment at an angular resolution of approximately 1.1 milliradians. This calculation is based on the fact that the outer segment of a single retinal photoreceptor cell is approximately 25 microns in radius, the effective focal length of the human eye is approximately 17 millimeters in an aqueous environment, and approximately 22 millimeters in air A light source having a viewing angle of 1.1 milliradians can be focused on a single retinal cell, so all of the power from the light source can be absorbed by the same cell. A light source having a smaller viewing angle than this is still absorbed by a single photoreceptor. However, due to low optical quality, a light source having a large viewing angle cannot be focused into a small spot. That is, it is impossible to focus such a light source onto a single biological cell, and as a result, the risk posed by a light source having a large viewing angle is reduced. In other words, a single retinal cell occupies approximately 4×10 steradians. Radiation from a diffused light source having a viewing angle of 1.5 steradians is expected to be distributed over at least two retinal cells, so the retinal risk is approximately halved and is safe. Referring now in detail to FIG. 7C, PV71a reflects a portion of the light that illuminates the PV in a diffused manner. A lens 75 is disposed 100 mm from the surface of the window in front of PV71a A light source having a viewing angle of 1.1 milliradians can be focused on a single retinal cell, so all of the power from the light source can be absorbed by the same cell. A light source having a smaller viewing angle than this is still absorbed by a single photoreceptor. However, due to low optical quality, a light source having a large viewing angle cannot be focused into a small spot. That is, it is impossible to focus such a light source onto a single biological cell, and as a result, the risk posed by a light source having a large viewing angle is reduced. In other words, a single retinal cell occupies approximately 4×10 steradians. Radiation from a diffused light source having a viewing angle of 1.5 steradians is expected to be distributed over at least two retinal cells, so the retinal risk is approximately halved and is safe. Referring now in detail to FIG. 7C, PV71a reflects a portion of the light that illuminates the PV in a diffused manner. A lens 75 is disposed 100 mm from the surface of the window in front of PV71a Referring now in detail to FIG. 7C, PV71a reflects a portion of the light that illuminates the PV in a diffused manner. A lens 75 is disposed 100 mm from the surface of the window in front of PV71a Referring now in detail to FIG. 7C, PV71a reflects a portion of the light that illuminates the PV in a diffused manner. A lens 75 is disposed 100 mm from the surface of the window in front of PV71a -6 steradians. Radiation from a diffused light source having a viewing angle of 1.5 steradians is expected to be distributed over at least two retinal cells, so the retinal risk is approximately halved and is safe. Referring now in detail to FIG. 7C, PV71a reflects a portion of the light that illuminates the PV in a diffused manner. A lens 75 is disposed 100 mm from the surface of the window in front of PV71a safe.

[0094] Referring now in detail to FIG. 7C, PV71a reflects a portion of the light that illuminates the PV in a diffused manner. A lens 75 is disposed 100 mm from the surface of the window in front of PV71a Referring now in detail to FIG. 7C, PV71a reflects a portion of the light that illuminates the PV in a diffused manner. A lens 75 is disposed 100 mm from the surface of the window in front of PV71a converges the light beam to a light spot 77 at the focal point of the lens. When PV71a is TE M 00 If it is assumed that the lens 75 reflects a high-quality light beam similar to a laser, the lens 75 focuses the light on a diffraction-limited spot. The angle 70 subtended between the top of the image, the center of the lens, and the bottom of the image is close to 0. The angle 70 subtended between the top of the image, the center of the lens, and the bottom of the image is close to 0. is close to 0.

[0095] Another possible scenario is shown in FIG. 7D. Here, instead of preserving the optical quality of the original laser beam, PV71a diffusely reflects the image. In such a case, the lens 75 does not generate a diffraction-limited spot, but rather generates an image 76 of PV71a, and the angle 70 is clearly larger. Instead of preserving the optical quality of the original laser beam, PV71a diffusely reflects the image. In such a case, the lens 75 does not generate a diffraction-limited spot, but rather generates an image 76 of PV71a, and the angle 70 is clearly larger. does not generate a diffraction-limited spot, but rather generates an image 76 of PV71a, and the angle 70 is clearly larger. is clearly larger.

[0096] The lens 75 typically positions the point of the minimum viewing angle of the beam by moving around the PV cell so as to approach and move away from the PV cell, and determines the viewing angle of the beam at a predetermined distance. The lens 75 typically positions the point of the minimum viewing angle of the beam by moving around the PV cell so as to approach and move away from the PV cell, and determines the viewing angle of the beam at a predetermined distance. and determines the viewing angle of the beam at a predetermined distance.

[0097] In addition to the above requirements, it is important that the PV responds to changes in the illumination level. The higher the beam power, the higher the responsiveness of the photovoltaic cell must be to allow a safety system based on the detection of the light level. It has been found that in order to increase the responsiveness of the PV, the structure of the cell needs to be adapted to match the intended power level according to the following equation. The higher the beam power, the higher the responsiveness of the photovoltaic cell must be to allow a safety system based on the detection of the light level. It has been found that in order to increase the responsiveness of the PV, the structure of the cell needs to be adapted to match the intended power level according to the following equation. It has been found that in order to increase the responsiveness of the PV, the structure of the cell needs to be adapted to match the intended power level according to the following equation. is found. 10 27 × (band gap) 2 A / d < 214 / P 3

[0098] Here, d is the thickness of the layer in the photovoltaic cell that absorbs the photons of the beam, measured in meters. is measured in meters.

[0099] The band gap is the band gap energy of the pn junction and is measured in joules. It is determined.

[0100] A is the area of the photovoltaic cell measured in square meters. 2 It is the area of the photovoltaic cell measured in square meters.

[0101] If the cell used is too large, the responsiveness of the cell decreases and it cannot respond at a sufficient speed to changes in the illumination level. It cannot respond at a sufficient speed to changes in the illumination level.

[0102] d is usually less than 300 microns thick and always less than 1000 microns thick, or this can be simplified as follows. It can be simplified as follows. 10 30 × (band gap) 2 A < 214 / P 3

[0103] Or, in a more convenient form, it is as follows. P 3 × (band gap) 2 A < 213 × 10 -30

[0104] Now refer to FIGS. 8A and 8B. FIG. 8A shows a reference PV cell 81a having known characteristics, and FIG. 8B shows the effect of the reflected collimated laser light on the human eye. In FIG. 8A, the light beam 84 illuminates the PV cell 81a, and most of the light is absorbed by the cell 81a, while a part of the incident beam is reflected by the cell towards the eye 85. The cell 81a typically reflects about 2 - 10% of the light impinging on the cell, and most of it is specular reflection. Here, the light hitting a flat surface creates a mirror-like reflection, and the angle of incidence is equal to the angle of return. The reflected light is collected by the lens 88 of the human eye 85 and forms several separate small lines. These lines are images of the conductors on the retina 86. FIG. 8B shows the effect of the reflected collimated laser light on the human eye. In FIG. 8A, the light beam 84 illuminates the PV cell 81a, and most of the light is absorbed by the cell 81a, while a part of the incident beam is reflected by the cell towards the eye 85. The cell 81a typically reflects about 2 - 10% of the light impinging on the cell, and most of it is specular reflection. Here, the light hitting a flat surface creates a mirror-like reflection, and the angle of incidence is equal to the angle of return. The reflected light is collected by the lens 88 of the human eye 85 and forms several separate small lines. These lines are images of the conductors on the retina 86. In FIG. 8A, the light beam 84 illuminates the PV cell 81a, and most of the light is absorbed by the cell 81a, while a part of the incident beam is reflected by the cell towards the eye 85. The cell 81a typically reflects about 2 - 10% of the light impinging on the cell, and most of it is specular reflection. Here, the light hitting a flat surface creates a mirror-like reflection, and the angle of incidence is equal to the angle of return. The reflected light is collected by the lens 88 of the human eye 85 and forms several separate small lines. These lines are images of the conductors on the retina 86. While most of the light is absorbed by the cell 81a, a part of the incident beam is reflected by the cell towards the eye 85. The cell 81a typically reflects about 2 - 10% of the light impinging on the cell, and most of it is specular reflection. Here, the light hitting a flat surface creates a mirror-like reflection, and the angle of incidence is equal to the angle of return. The reflected light is collected by the lens 88 of the human eye 85 and forms several separate small lines. These lines are images of the conductors on the retina 86. The cell 81a typically reflects about 2 - 10% of the light impinging on the cell, and most of it is specular reflection. Here, the light hitting a flat surface creates a mirror-like reflection, and the angle of incidence is equal to the angle of return. The reflected light is collected by the lens 88 of the human eye 85 and forms several separate small lines. These lines are images of the conductors on the retina 86. Here, the light hitting a flat surface creates a mirror-like reflection, and the angle of incidence is equal to the angle of return. The reflected light is collected by the lens 88 of the human eye 85 and forms several separate small lines. These lines are images of the conductors on the retina 86. The reflected light is collected by the lens 88 of the human eye 85 and forms several separate small lines. These lines are images of the conductors on the retina 86. These lines are images of the conductors on the retina 86.

[0105] As shown in FIG. 8B, the cornea and the lens can focus the light 89 from the collimated beam into a small spot, which can cause a large local damage. The divergence of the reflection from the collimated beam is minimal, and since the beam is refracted by both the cornea 87 and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. ups, which can cause a large local damage. The divergence of the reflection from the collimated beam is minimal, and since the beam is refracted by both the cornea 87 and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86.

[0106] Now, refer to FIG. 8C which schematically shows the PV cell 81b according to the implementation of the present disclosure. In contrast to the PV cell 81a, the PV cell 81b uses a conductor 82b and a cover layer 83 with a non-rectangular and highly convex contour. The cell 81b generally includes a conductor 82b that reflects up to about 10% of the light. This conductor is wider than a typical rectangular conductor, but since the conductor 82b reflects the beam at a certain angle, most of the primary reflections are above the total internal reflection angle of the optical cover layer, and thus are reflected back towards the cell, where about 90% of it is absorbed. and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. and the lens 88, it results in the focusing of a powerful beam of light energy that can converge on sensitive eye tissues as shown in FIG. 7C. Such a focused beam has a significant potential to cause damage 80 at the point 80 where the beam impinges on the retina 86. and thus are reflected back towards the cell, where about 90% of it is absorbed. About 0.04% - 2% of the original beam is reflected a second time by the conductor, and these light rays 89b can be reflected outside the optical cover layer 83, but here they are reflected in a diffused manner. The lens 88 of the eye can collect a small amount of the diffused emitted light 89b and form an image of the cell 81b on the retina. However, since the power per unit area of the image is extremely small, the risk to the retina is also extremely small. The maximum collection of light by the eye occurs at the minimum distance. Since the minimum focal distance of the human eye is about 100 - 150 mm, the most dangerous collection position is from the cell. and thus are reflected back towards the cell, where about 90% of it is absorbed. and form an image of the cell 81b on the retina. However, since the power per unit area of the image is extremely small, the risk to the retina is also extremely small. The maximum collection of light by the eye occurs at the minimum distance. Since the minimum focal distance of the human eye is about 100 - 150 mm, the most dangerous collection position is from the cell. and form an image of the cell 81b on the retina. However, since the power per unit area of the image is extremely small, the risk to the retina is also extremely small. The maximum collection of light by the eye occurs at the minimum distance. Since the minimum focal distance of the human eye is about 100 - 150 mm, the most dangerous collection position is from the cell. and form an image of the cell 81b on the retina. However, since the power per unit area of the image is extremely small, the risk to the retina is also extremely small. The maximum collection of light by the eye occurs at the minimum distance. Since the minimum focal distance of the human eye is about 100 - 150 mm, the most dangerous collection position is from the cell. and form an image of the cell 81b on the retina. However, since the power per unit area of the image is extremely small, the risk to the retina is also extremely small. The maximum collection of light by the eye occurs at the minimum distance. Since the minimum focal distance of the human eye is about 100 - 150 mm, the most dangerous collection position is from the cell. It is present at a distance of approximately 100 to 150 mm.

[0107] The reflected light from the reference PV cell in FIG. 8A is compared with the implementation of the present disclosure schematically depicted in FIG. 8C When compared, the beam 84 approaches the cell 81b at the same angle as shown to impinge on the cell 81a. In contrast, in FIG. 8C, after the beam crosses the cover layer 83, it is reflected by the conductor 82b at an angle greater than 80% of the critical angle, as calculated based on the reflectivity of the lower part of the cover layer 83. The reflected ray is absorbed by the cell 81b with higher efficiency compared to the cell 81a, and the percentage of the beam finally emitted through the upper part of the optical cover layer 83 is low compared to the percentage reflected by the conductor 82a. Furthermore, the light ray 89b emitted from the upper part of the optical cover layer 83 diffuses and is emitted in different directions. Therefore, the power of the light impinging on the eye 85 in FIG. 8C is lower compared to the power of the light collected by the eye 85 in FIG. 8A. In FIG. 8C, since these light rays do not travel in the same direction, they do not converge at the same position, and thus form a diffused image on the retina of the eye 85 with a much lower risk to the retina, as shown in FIG. 7D.

[0108] The devices described herein typically enable cells of 1 cm × 1 cm size to reflect diffused retroreflection, so that the reflection of the beam of a TEM 00 laser from the conductor is focused by a f = 25 mm lens placed 100 mm from the surface of the cell, and when focused, subtends at least 1.5 mRad at its 1 / e diameter, typically It forms a minimum image that is much larger. Therefore, the risk to the retina is much less. Further, by diffusing the beam, the cell configuration of the present invention makes it possible to make the typically centrally weighted beam received from a laser source less concentrated and uniform. That is, by improving the uniformity of illumination, current can flow from a short distance to the current collector at the periphery of the cell, enabling full utilization of the cell. The cell of the present invention can also thicken the metal conductive fingers, resulting in lower resistance losses, which is an advantageous feature in the case of high beam fluxes and applies to most laser power

[0109] Referring now to FIG. 9, it is assumed that a transmitter 95, typically a laser, is directing a beam of a given power in the direction of a receiver 91, but the receiver has not received all or part of that power, indicating a situation where the beam is directed in an unintended direction. A safety control system 90 is shown that is configured to give a warning. The control system 90 indicates or warns that the transmitted laser beam may pose a danger to the surroundings depending on whether it has reached its intended receiver or has reached the correct receiver but with excessively reduced power. The controller unit 97 is most advantageously placed in the transmitter 95, but as shown in FIG. 9, it may be placed at other locations in the system or in the space served by the transmitter and receives a signal input 92 from a detection unit 91 at the receiver. This is generally a PV cell Even in a situation where a significant level of power can impinge on the PV cell 91, the illumination having the laser wavelength represents that portion of the power level impinging on the PV cell. The control unit 97 is also configured to receive a signal from the laser power supply 95 in the transmitter. Such a signal indicates a signal indicating the power of the laser beam emitted from the position of the scan mirror 96 by the laser, and the settings of both of these system components are determined by the operating requirements for supplying the beamized laser power to the receiver. When the laser power setting and the mirror scan position indicate that a predetermined power level is predicted from the detector unit, and the actual input to the control unit indicates a power level below the predicted level by exceeding a predetermined amount, a part of the beam is assumed to be obstructed and not reaching the intended receiver target, so a safety warning by the system is activated. It should be understood that the control system can also optimize the settings of the scan mirror in response to the power measured by the detector unit, keep the laser beam focused on the receiver PV, and control the laser to supply the intended laser power in its conventional manner, i.e., it can also operate in the reverse direction. As will be apparent to those skilled in the art, the present invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and sub - combinations of the various features described above, as well as variations and modifications that will occur to those skilled in the art upon reading the above description but do not exist in the prior art. represents that portion of the power level impinging on the PV cell of the illumination having the laser wavelength. The control unit 97 is also configured to receive a signal from the laser power supply 95 in the transmitter. Such a signal indicates a signal indicating the power of the laser beam emitted from the position of the scan mirror 96 by the laser, and the settings of both of these system components are determined by the operating requirements for supplying the beamized laser power to the receiver. indicates a signal indicating the power of the laser beam emitted from the position of the scan mirror 96 by the laser, and the settings of both of these system components are determined by the operating requirements for supplying the beamized laser power to the receiver. signal, and the settings of both of these system components are determined by the operating requirements for supplying the beamized laser power to the receiver. The laser power setting and the mirror scan position are determined by the operating requirements for supplying the beamized laser power to the receiver. When the laser power setting and the mirror scan position indicate that a predetermined power level is predicted from the detector unit, and the actual input to the control unit indicates a power level below the predicted level by exceeding a predetermined amount, a part of the beam is assumed to be obstructed and not reaching the intended receiver target, so a safety warning by the system is activated. When the laser power setting and the mirror scan position indicate that a predetermined power level is predicted from the detector unit, and the actual input to the control unit indicates a power level below the predicted level by exceeding a predetermined amount, a part of the beam is assumed to be obstructed and not reaching the intended receiver target, so a safety warning by the system is activated.

[0110] It should be understood that the control system can also optimize the settings of the scan mirror in response to the power measured by the detector unit, keep the laser beam focused on the receiver PV, and control the laser to supply the intended laser power in its conventional manner, i.e., it can also operate in the reverse direction. and control the laser to supply the intended laser power in its conventional manner, i.e., it can also operate in the reverse direction. and control the laser to supply the intended laser power in its conventional manner, i.e., it can also operate in the reverse direction.

[0111] As will be apparent to those skilled in the art, the present invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and sub - combinations of the various features described above, as well as variations and modifications that will occur to those skilled in the art upon reading the above description but do not exist in the prior art. including variations and modifications that will occur to those skilled in the art upon reading the above description but do not exist in the prior art.

Claims

1. A power conversion device that converts optical power into electrical power suitable for optical wireless power transmission using a laser beam. Vice, a photovoltaic cell having a plurality of conductors on a surface adapted to receive the laser beam. At least one contact having a band gap energy of 0.75 eV to 1.2 eV. a photovoltaic cell having a junction; a cover layer disposed on the photovoltaic cell; Including, The cover layer absorbs or blocks the transmission of illumination having wavelengths outside the range of the wavelengths of the laser beam. The laser beam is transmitted to the photovoltaic cell by either limiting or reflecting the laser beam. The material may be adapted to the laser beam has a wavelength of 700 nm to 1500 nm; The wavelength of the illumination outside the wavelength range of the laser beam is in the range of 550 nm to 700 nm. 、 The transmittance of the cover layer with respect to the wavelength of the laser beam is in the range of 550 nm to 700 nm. at least 50% higher than the transmittance of the cover layer for wavelengths within the range The power conversion device has a conversion efficiency to electrical power at the wavelength of the laser beam of 550 nW or less. A power conversion device having a conversion efficiency to electrical power at a wavelength of at least 2.5 times higher than that of the conventional power conversion device. 。

2. The band gap energy is at least 25% longer than the wavelength of the laser. The efficiency of conversion of optical power to electrical power for any wavelength is 4 times higher than the efficiency at the laser wavelength.

2. The method of claim 1, wherein the wavelength of the laser is tuned to be more than twice as small as the Power conversion device.

3. The cover layer further comprises: a first anti-reflective coating disposed on a surface of the cover layer remote from the photovoltaic cell; and reflecting illumination having a wavelength outside the range of the wavelength of the laser beam. a first anti-reflective coating adapted to transmit light to the cover layer; a second anti-reflective coating disposed between a surface of the photovoltaic cell and the cover layer. The laser beam is then deflected by reflecting illumination having a wavelength outside the wavelength range of the laser beam. a second anti-reflective coating adapted to transmit The power conversion device according to claim 1 or 2, Chair.

4. A safety system for a wireless optical power transmission system including a transmitter, a receiver and a control unit. hand, (i) the transmitter; a laser adapted to emit a beam; a scan mirror adapted to steer the beam to the receiver; Including, (ii) the receiver comprises: a photovoltaic cell having a plurality of conductors on a surface adapted to receive the laser beam. At least one contact having a band gap energy of 0.75 eV to 1.2 eV. a photovoltaic cell having a junction; a cover layer disposed on the photovoltaic cell; Including, The cover layer absorbs or reflects illumination having wavelengths outside the range of the wavelengths of the laser beam. a photovoltaic cell that is adapted to transmit the laser beam to the photovoltaic cell by restricting the laser beam through any of the following: The material includes (iii) the control unit receives first data representative of a position of the scan mirror; receiving second data from the transmitter representative of a power of the beam emitted by the laser; determining an expected power incident on the photovoltaic cell from the first data and the second data; , the predicted power and the laser impinging on the receiver measured by the photovoltaic cell. and comparing the predicted power to the power of the beam if the predicted power exceeds a predetermined level from the measured power. A safety system adapted to indicate possible safety hazards in the event of deviation from a given threshold.

5. A wireless optical power transmission system including a transmitter and a receiver, a laser adapted to emit a beam; a scan mirror adapted to steer the beam to the receiver; receiving a signal from a detection unit at the receiver; (i) detecting a beam emitted by the laser; and (ii) a position of the scan mirror. The control unit and Including, The receiver includes an optical receiver having a plurality of conductors on a surface adapted to receive the laser beam. A photovoltaic cell comprising at least one ferroelectric material having a band gap energy of 0.75 eV to 1.2 eV. a photovoltaic cell having at least one junction; The photovoltaic cell is adapted to detect the power of the laser beam reaching the photovoltaic cell. Adapted, the receiver includes a cover layer disposed on the photovoltaic cell; The cover layer is The laser beam absorbs or reflects illumination having a wavelength outside the wavelength range of the laser beam. a material adapted to transmit light from the light source to the photovoltaic cell; (i) a first anti-reflective coating disposed on a surface of the cover layer remote from the photovoltaic cell; a reflector for reflecting illumination having a wavelength outside the wavelength range of the laser beam, a first anti-reflective coating adapted to transmit the laser beam to the cover layer; teeth (ii) a second anti-reflective coating disposed between a surface of the photovoltaic cell and the cover layer; a reflector for reflecting illumination having a wavelength outside the wavelength range of the laser beam, a second anti-reflective coating adapted to transmit the laser beam to the photovoltaic cell; At least one of them Including, The detection unit detects the wavelength of the laser beam independently of other illumination. generating a signal representative of the power of the impinging laser beam; The control unit (i) controls the beam and (ii) a wireless optical system adapted to control at least one of the positions of the scan mirror; Power transmission system.

6. A power conversion device that converts optical power into electrical power suitable for optical wireless power transmission using a laser beam. Vice, At least one junction having a band gap energy between 0.75 eV and 1.2 eV a power conversion device having an outer layer through which laser light is transmitted to said one junction; a power conversion device having The outer layer is exposed from any direction between ±20° with respect to the normal line of the surface of the outer layer. at least a first wavelength with at least 80% efficiency when illuminated through said one configured to penetrate to a junction of The power conversion device has a conversion efficiency of at least 30%, and the first wavelength is 700 nm. a near-infrared wavelength of 1500 nm to 1,500 nm; The outer layer of the power conversion device is configured to receive a second wavelength of incident illumination between 550 nm and 700 nm. a reflecting or absorbing portion of the second wavelength, wherein less than 60% of the illumination at the second wavelength passes through the outer layer. When illuminated through the outer layer from any direction between ±20° to the normal to the surface of a power conversion device for the second wavelength reaching the at least one junction; The conversion efficiency is less than 20%; and The outer layer of the power conversion device absorbs at least a third wavelength between 300 nm and 550 nm. and configured to reflect or absorb light in any direction between ±20° relative to the normal to the surface of the outer layer. before reaching the at least one joint when irradiated through the outer layer from At least 50% of the power of the third wavelength is absorbed, and the power for the third wavelength is The conversion efficiency of the conversion device is less than 10%; and The conversion efficiency of the power conversion device for a fourth wavelength of 1500 nm to 2000 nm is 5. % or less a power conversion device,

7. 1. A power conversion device for converting an optical power beam into electrical power, comprising: a semiconductor device having a pn junction adapted to absorb the optical power beam; a top conductor and a bottom conductor in electrical contact with the semiconductor device, the top conductor being top and bottom conductors covering a portion of a top surface of the semiconductor device; an optical layer disposed on a top surface of the semiconductor device, the optical layer having an upper volume and a lower volume; the lower volume being in optical contact with a top surface of the semiconductor device, the upper volume is in optical contact with air; Layers and Including, The top conductor is adapted to reflect at least 30% of the light impinging on the top conductor. R, the optical layer has an optical density for the optical power beam of less than 2; The top conductor reflects at least 25% of the light reflected by the top conductor at a rate of sin －１ A power conversion device adapted to be oriented at an angle greater than (1 / refractive index of the lower volume). Chair.

8. At least a portion of the light reflected by the conductor is reflected back from the top surface of the upper volume.

8. The power conversion device of claim 7, wherein the light is reflected at an angle to receive the reflected light.

9. The upper volume of the optical layer is exposed to the optical power beam coming from a medium with a refractive index of approximately unity.

9. The optical fiber according to claim 7 or 8, wherein the optical fiber is an anti-reflective coating adapted to reduce the reflection of the optical fiber.

13. A power conversion device according to any one of claims 1 to 12.

10. 10. Any of claims 7 to 9, wherein the upper volume of the optical layer is a scratch-resistant coating.

13. A power conversion device according to any one of claims 1 to 12.

11. The light beam extends over an angle of at least −10 degrees to +10 degrees relative to a normal to the top surface.

10. The power conversion device of claim 9, further adapted to reduce reflection of the power beam. Chair.

12. The coverage ratio of the upper layer covered by the upper conductor is at least 4%. Item 12. A power conversion device according to any one of items 7 to 11.

13. The power conversion device according to any one of claims 7 to 12, wherein the conductor is made of metal. Chair.

14. The power supply of claim 13, wherein the conductor comprises at least in part aluminum, gold, silver or copper. Conversion device.

15. The top surface of the semiconductor device is at least sin －１ (1 / refractive index of the lower volume) The area of ​​the geometric projection of the portions of the conductor that are aligned at an angle is equal to the area of ​​the semiconductor device. multiplied by the coverage ratio of the top surface covered by the top conductor, %. %.

16. 16. Any of claims 7 to 15, wherein the laser reflection from the power conversion device is diffusive.

13. A power conversion device as claimed in any preceding claim.

17. The diffuse reflection from the power conversion device has a visual angle of at least 1.5 milliradians.

17. The power conversion device of claim 16, comprising:

18. Meters ２ a surface area of ​​said semiconductor device measured in Joules squared, multiplied by the bandgap of the junction measured in watts to determine the cell's design maximum Multiplying the power by the cube is P ３ × (band gap) ２ A < 214 x 10 －３０ Like 214 x 10 －３０ 18. The power converter according to claim 7, Conversion device.

19. 19. Any of claims 7 to 18, wherein the top conductor comprises a conductive grid having a finger-shaped profile.

3. A power conversion device according to claim 1 .

20. 19. The method of claim 7, wherein the top conductor comprises a conductive grid having a triangular shaped profile.

13. A power conversion device as claimed in any one of the claims.

21. A power conversion device that converts optical power into electrical power suitable for optical wireless power transmission using a laser beam. Vice, a photovoltaic cell having a plurality of conductors on a surface adapted to receive the laser beam; 、 The photovoltaic cell comprises at least one photovoltaic cell having a band gap energy of 0.75 eV to 1.2 eV. at least one joint and a cover layer disposed at the joint, The cover layer is configured to absorb or reflect illumination having a wavelength in the range of 550 nm to 700 nm. and adapted to transmit the laser beam toward the photovoltaic cell. The material includes the laser beam has a wavelength of 700 nm to 1500 nm; The transmittance of the cover layer for the wavelength of the laser beam is 550 nm to 700 nm at least 50% higher than the transmittance of the cover layer for wavelengths in the range The power conversion device has a conversion efficiency of the laser beam to electrical power at the wavelength of the laser beam of A power conversion device with a conversion efficiency to power at least 2.5 times greater than that at 550 nm. Chair.

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