Photoelectric detector

Abstract

The invention relates to a photoelectric detector which comprises a light absorption layer, and the thickness of the light absorption layer is 500-1500 nm. According to the photoelectric detector provided by the invention, through optimal design of the thickness and energy level distribution of the perovskite absorption layer, the responsivity and efficiency of the photoelectric detector are remarkably improved, and the problem of insufficient light absorption caused by too small thickness or composite loss caused by too large thickness is avoided.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic detection technology, and in particular, to an optoelectronic detector. Background Art

[0002] An optoelectronic detector is a core optoelectronic device that can convert optical signals into electrical signals and is widely used in modern optoelectronics. Traditional optoelectronic detectors mostly use semiconductor materials such as silicon and gallium arsenide. These materials have mature preparation technologies and excellent performance. However, the preparation processes of these materials are complex, the costs are high, and the response efficiency in a specific wavelength band (such as the near-infrared region) is low, which limits their application in next-generation optoelectronic devices.

[0003] In recent years, perovskite materials have received extensive attention due to their excellent optical and electrical properties. Perovskite has advantages such as a high absorption coefficient, a long carrier lifetime, and a high mobility. At the same time, its preparation process is simple and the cost is low, so it has become a research hotspot in the field of optoelectronic detectors. In particular, organic-inorganic hybrid perovskite (ABX 3 , where A is an organic or inorganic cation, B is a metal cation, and X is a halogen anion) exhibits excellent light absorption performance and can cover the ultraviolet, visible, and near-infrared spectral ranges.

[0004] Currently, optoelectronic detectors based on perovskite materials mostly adopt pn junction or pin junction structures: the pn junction structure is simple, but its carrier separation efficiency is low, which limits the output of photocurrent; while the pin structure effectively reduces the recombination loss and improves the responsivity of the optoelectronic detector by introducing an intrinsic layer.

[0005] However, the thickness of the perovskite absorption layer has a significant impact on the quantum efficiency of the detector: being too thin will result in insufficient light absorption, and being too thick will increase carrier recombination. Therefore, how to optimize the thickness of the perovskite absorption layer to maximize the quantum efficiency is the key issue for improving the performance of optoelectronic detectors. Summary of the Invention

[0006] In view of this, the present invention provides an optoelectronic detector.

[0007] Specifically, the present invention is implemented through the following technical solutions:

[0008] According to a first aspect of the present invention, there is provided an optoelectronic detector, including: a light absorption layer, and the thickness of the light absorption layer is 500 - 1500 nm.

[0009] Optionally, the light absorption layer is a perovskite absorption layer.

[0010] Optionally, the thickness of the light absorption layer is 500 - 1000 nm.

[0011] Optionally, the thickness of the light absorption layer is 900 nm.

[0012] Optionally, the perovskite absorption layer is made of a perovskite material having a wide bandgap ABX 3 type structure, where A is an organic cation or an inorganic cation, B is a transition metal cation, and X is a halogen anion.

[0013] Optionally, it further includes: a top layer disposed on the light absorption layer.

[0014] Optionally, the top layer is a pin junction structure layer.

[0015] Optionally, it further includes: an electrode disposed on the light absorption layer.

[0016] Optionally, it further includes: a buffer layer disposed between the electrode and the light absorption layer.

[0017] Optionally, the electrode is a metal electrode or a transparent conductive oxide electrode.

[0018] The technical solution provided by the present invention at least brings the following beneficial effects:

[0019] A photodetector provided by the present application significantly improves the responsivity and efficiency of the photodetector through the optimized design of the thickness and energy level distribution of the perovskite absorption layer, and avoids the problems of insufficient light absorption caused by too thin a thickness or recombination loss problems caused by too thick a thickness. Description of the Drawings

[0020] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention.

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic structural diagram of the top layer in a photodetector provided by an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the photocurrent output of the top layer in a photodetector provided by an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the quantum efficiency and the absorption layer thickness of a photodetector provided by an embodiment of the present invention;

[0025] Figure 4 Schematic diagram of the energy level position and light incident depth of a photodetector provided by an embodiment of the present invention. Detailed implementation manners

[0026] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Figure 1 Schematically shows a photodetector applicable to an embodiment of the present invention, which is a pin-structured photodetector; and a comparative photodetector, which is a pn-structured photodetector.

[0028] Embodiment

[0029] Referring to Figure 1 As shown, the present application provides a pin-structured photodetector, including: a transparent conductive electrode, a hole transport layer, a perovskite absorption layer, an electron transport layer and a back electrode.

[0030] Exemplarily, it includes: a transparent conductive electrode, which is disposed on the topmost layer.

[0031] The electrode is disposed on the topmost layer for collecting photo-generated carriers and converting them into electrical signals for output. The electrode can be a metal electrode or a transparent conductive oxide electrode, and the specific selection depends on the application scenario and performance requirements of the photodetector.

[0032] Exemplarily, it includes: a hole transport layer (p-type), which is disposed between the transparent conductive electrode and the perovskite absorption layer.

[0033] Its main function is to transport holes and block electrons, thereby improving the charge separation efficiency. Common hole transport layer materials include poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), molybdenum trioxide (MoO3), etc.

[0034] Exemplarily, it further includes: a light absorption layer, and the thickness of the light absorption layer is 500 - 1500 nm.

[0035] The thickness of the light absorption layer is 500 - 1500 nm. The selection of this range is to balance the sensitivity and response speed of the photodetector. A thicker absorption layer can absorb more photons and improve sensitivity, but it may also increase the recombination probability and diffusion time of photo-generated carriers, affecting the response speed. Therefore, the specific thickness needs to be optimized according to the actual application requirements.

[0036] Exemplarily, the light absorption layer is a perovskite absorption layer.

[0037] Exemplarily, the thickness of the light absorption layer is 500 - 1000 nm.

[0038] Exemplarily, the thickness of the light absorption layer is 900 nm.

[0039] The thickness of the specific value 900 nm is the optimal value obtained through simulation and experimental verification in a specific application scenario to achieve the best compromise between sensitivity and response speed.

[0040] Exemplarily, the perovskite absorption layer is made of a perovskite material, and the perovskite material has a wide-bandgap ABX 3 type structure, where A is an organic cation or an inorganic cation, B is a transition metal cation, and X is a halogen anion.

[0041] The perovskite material has a wide-bandgap ABX 3 type structure, where A is an organic cation or an inorganic cation, B is a transition metal cation, and X is a halogen anion. As a light absorption layer, this material has excellent optoelectronic properties, such as a high absorption coefficient, a long carrier diffusion length, and a low defect density, etc., which helps to improve the performance of the photodetector. Perovskite photodetectors usually have a fast response speed and high sensitivity, and at the same time, the spectral response range can be optimized by adjusting the composition and structure of the perovskite material.

[0042] Exemplarily, it further includes: an electron transport layer (n-type), and the electron transport layer is disposed under the light absorption layer.

[0043] The electron transport layer is disposed under the light absorption layer, and its main function is to transport electrons and block holes. Common electron transport layer materials include titanium dioxide (TiO2), zinc oxide (ZnO), etc.

[0044] Exemplarily, the bottom layer is a back electrode.

[0045] The back electrode is usually located at the end of the detector, used to collect the electrons generated by the perovskite absorption layer and export them as electrical signals. Common back electrode materials include metal electrodes (such as gold, silver, aluminum, etc.).

[0046] The pin junction structure layer is set as the top layer on the light absorption layer, which helps to improve the response speed and sensitivity of the photodetector. The pin diode is composed of an intrinsic (or lightly doped) layer sandwiched between a heavily doped P layer and an N layer. The i layer (intrinsic layer) serves as the depletion region, which can efficiently and rapidly separate and collect photo-generated carriers, thus obtaining a high-frequency response.

[0047] Comparative example

[0048] Refer to Figure 1 As shown, the pn junction photodetector structure is similar to the pin structure photodetector. The difference is that the pn junction photodetector does not have a hole transport layer and an electron transport layer, but has two absorption layers, including a p-type absorption layer and an n-type transport layer. The p-type absorption layer and the n-type transport layer have the same thickness, and the sum of the thicknesses of the two layers is the same as the thickness of the absorption layer of the pin structure photodetector.

[0049] In summary, for the photodetector of this application, the analysis is as follows:

[0050] 1. Optimization of the photodetector structure

[0051] By optimizing the structure of the photodetector from the pn junction to the pin structure, its performance can be significantly improved. This structural optimization enables the additional hole transport layer (HTL) and electron transport layer (ETL) to help separate and transport carriers more efficiently, reducing the recombination loss of carriers during the transport process. Experimental results show that within all applied voltage ranges, the photocurrent value of the pin structure is significantly higher than that of the pn structure, which reflects the advantage of the pin structure in photodetection performance. In addition, the asymmetry of the current-voltage curves of the two structures under positive and negative voltages reveals the differences in the electric field distribution and carrier transport characteristics, and the pin structure is more conducive to improving the carrier collection efficiency. Therefore, the pin structure, as the core architecture of the photodetector, can significantly enhance the photocurrent output and meet the requirements for high-performance photodetectors.

[0052] 2. Optimization of the thickness of the light absorption layer

[0053] The thickness of the light absorption layer has an important impact on the performance of the photodetector. If the thickness is too thin, it may lead to insufficient light absorption, causing the detector to fail to capture enough light signals, thus reducing the responsivity and efficiency. If the thickness is too thick, it may cause recombination loss problems, that is, photo-generated carriers may be lost due to recombination during the transport process, which will also affect the performance of the detector. This photodetector optimizes the thickness of the perovskite absorption layer to be in the range of 500 - 1500 nm, thus avoiding the above two problems. Within this thickness range, the perovskite material can fully absorb light signals, and the recombination loss of photo-generated carriers is relatively low, thus ensuring the high responsivity and high efficiency of the detector.

[0054] 3. Optimization of Energy Level Distribution

[0055] In addition to thickness optimization, this photodetector also focuses on the design of the energy level distribution of the perovskite absorption layer. Through reasonable energy level arrangement, the separation and transport of photo-generated carriers can be promoted, further improving the performance of the detector. Specifically, the energy band structure can be optimized by introducing a transport layer, a blocking layer, or a heterojunction, etc. For example, inserting a transport layer between the perovskite absorption layer and the electrode can reduce the interfacial reaction and promote the effective separation of carriers. At the same time, the presence of the transport layer can also block the reverse injection of charges, inhibit the ion migration phenomenon, and reduce the dark current.

[0056] 4. Performance Improvement of the Photodetector

[0057] Due to the above-mentioned optimized design, the photodetector has been significantly improved in terms of responsivity and efficiency. Specifically, the optimized perovskite absorption layer can absorb light signals more fully and convert them into electrical signals. At the same time, the reasonable energy level distribution design promotes the separation and transport of photo-generated carriers, reducing the influence of recombination loss and dark current.

[0058] 5. Application Scenarios and Prospects

[0059] This photodetector has broad application prospects and can be applied to fields such as optical communication, spectral analysis, and medical imaging. In these fields, a photodetector with high responsivity and high efficiency is one of the key components for realizing high-performance systems. In addition, with the continuous in-depth research on perovskite materials and the continuous improvement of the preparation process, the performance of this photodetector is expected to be further improved. For example, by improving the preparation process to enhance the crystallinity and uniformity of perovskite materials, thereby further improving the photoelectric conversion efficiency and stability of the detector.

[0060] The core structure of a photodetector provided by this application includes: a transparent conductive electrode, a hole transport layer, a perovskite absorption layer, an electron transport layer, and a back electrode. Transparent conductive electrode: Usually located at the front end of the detector, it is used to receive and transmit incident light, and at the same time collect charges as an electrode. Common transparent conductive electrode materials include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), etc. Hole transport layer: Located between the transparent conductive electrode and the perovskite absorption layer, its main function is to transport holes and block electrons, thereby improving the charge separation efficiency. Common hole transport layer materials include poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), molybdenum trioxide (MoO3), etc. Perovskite absorption layer: As the core part of the detector, it is responsible for absorbing photons and generating photo-generated carriers (electrons and holes). Its thickness and energy level distribution have an important impact on the performance of the detector. Electron transport layer: Located between the perovskite absorption layer and the back electrode, its main function is to transport electrons and block holes. Common electron transport layer materials include titanium dioxide (TiO2), zinc oxide (ZnO), etc. Back electrode: Usually located at the end of the detector, it is used to collect the electrons generated by the perovskite absorption layer and export them as electrical signals. Common back electrode materials include metal electrodes (such as gold, silver, aluminum, etc.).

[0061] The performance optimization is designed and implemented through the following simulation calculation methods, and the related theories are as follows:

[0062] When the incident photon has an energy , the photon is absorbed by the material, exciting the electrons in the valence band to transition to the conduction band, forming electron-hole pairs. The generation rate of photo-generated carriers is described by the formula:

[0063]

[0064] The generation rate g reg depends on the energy of the photon the band gap E of the material g , and the effective mass m of the carriers * .

[0065] During this process, the complex dielectric constant (∈ r =∈′ r +i∈″ r ) of the material will be corrected, and the real part (Δ∈′ r ) and the imaginary part (Δ∈″r) are determined by absorption and optical response respectively:

[0066]

[0067] The distribution of the generated carriers in the conduction band and the valence band is described by the Fermi distribution functions f c and f v :

[0068]

[0069] Among them, electrons and holes accumulate near the bottom of the conduction band and the top of the valence band respectively, and are determined by the quasi-Fermi levels E Fn and E Fp .

[0070] The distributions of these quasi-Fermi levels also affect the intensity of the optical transition dipole moment, and its average value is related to the optical properties of the material and the spontaneous emission lifetime:

[0071]

[0072] The generated electrons and holes may recombine in the material, and the recombination rate is described by the drift-diffusion equation:

[0073]

[0074] where R n and R p include the stimulated recombination rate R stim :

[0075]

[0076] Recombination reduces the number of photo-generated carriers, but the applied electric field separates electrons and holes, inhibits recombination, and thus forms a photocurrent.

[0077] In a photodetector, photo-generated carriers are collected under an applied bias voltage to form a photocurrent J photo。 The magnitude of the photocurrent is determined by the generation rate g red of photo-generated carriers, the diffusion length of carriers, the recombination rate R n , and the absorption characteristics (Δ∈″ r ) of the material.

[0078] The optical response characteristics (quantum efficiency) can be further analyzed through the recombination rate and the optical properties of the material. The quantum efficiency η of a photodetector is defined as:

[0079]

[0080] In the formula, it is closely related to R stim and .

[0081] As Figure 1 shown, through finite element simulation, it is found that compared with the traditional pn junction structure, the pin junction structure can effectively reduce carrier recombination and improve carrier separation efficiency, thus significantly enhancing the photocurrent output. Optimized quantum efficiency: The thickness of the perovskite absorption layer significantly affects the quantum efficiency.

[0082] AsFigure 2 As shown, the dark curve represents the photocurrent output of a photodetector based on a pn junction structure, and the light curve represents the photocurrent output of a pin structure photodetector. The variation trend of the current value with the applied voltage shows the performance differences between the two structures. In all ranges of the applied voltage, the photocurrent value of the pin structure is significantly higher than that of the pn structure. This is because the additional hole transport layer (HTL) and electron transport layer (ETL) in the pin structure contribute to more efficient carrier separation and transport, reducing the recombination loss. The current-voltage curves of the two structures show a certain asymmetry under positive and negative voltages, reflecting the differences in the electric field distribution and carrier transport characteristics. The pin structure is more suitable as the core architecture of the photodetector, which can significantly improve the photocurrent output and meet higher performance requirements.

[0083] As Figure 3 shown, the horizontal axis is the thickness of the perovskite absorption layer (unit: nm), and the vertical axis is the quantum efficiency. The curve shows the variation trend of the quantum efficiency with the thickness. The quantum efficiency first increases and then decreases with the increase of the thickness, and there is a maximum value. An overly thin perovskite layer (<500 nm) results in a low quantum efficiency due to insufficient light absorption; while an overly thick perovskite layer (>1200 nm) has an increased recombination loss due to the limited carrier diffusion length, reducing the quantum efficiency.

[0084] When the perovskite thickness is about 1000 nm, the quantum efficiency reaches the maximum value (about 0.143), indicating that the light absorption and carrier transport are in the best balance state at this time. Optimizing the thickness of the perovskite absorption layer is crucial for improving the efficiency of the photodetector. It is recommended to control the perovskite thickness within a range close to the optimal value (900 nm) in the actual device.

[0085] As Figure 4 shown, the horizontal axis is the depth, and the vertical axis is the energy level, showing the distribution of the energy levels inside the device with depth. There are obvious bends in the conduction band and valence band within the perovskite layer, indicating the existence of an internal electric field. This electric field helps the separation of carriers, with electrons moving towards the ETL and holes moving towards the HTL. The spacing between the electron quasi-Fermi level and the hole quasi-Fermi level (gray line) represents the open-circuit voltage. The magnitude of this spacing indicates that the photo-generated potential of the device is close to the ideal value, further verifying the effect of thickness optimization. In the middle region of the perovskite layer, there is less carrier recombination, so the quasi-Fermi level distribution is relatively flat; while near the interface, due to the influence of interface states, there are slight changes in the quasi-Fermi level.

[0086] A method for calculating a photodetector provided in this application using finite element simulation. It is found through calculations using wave optics and semiconductor modules that under optimal thickness conditions, the perovskite absorption layer has an ideal energy level structure and electric field distribution, ensuring efficient carrier separation and transport. The optimization of the energy level distribution directly promotes the improvement of device performance. By introducing an electron transport layer and a hole transport layer, the pin structure can more efficiently separate and transport photo-generated carriers, thereby achieving a higher photocurrent output.

[0087] Compared with the pn junction, the pin structure introduces a hole transport layer (HTL) and an electron transport layer (ETL) on both sides of the perovskite absorption layer, forming a symmetric electric field distribution and improving the separation and collection efficiency of carriers. Thickness optimization: By changing the thickness of the perovskite absorption layer and combining the simulation results of quantum efficiency, the optimal thickness range is determined to ensure the balance between light absorption ability and carrier transport efficiency. Quantum efficiency simulation shows that when the thickness is about 900 nm, the detector performance reaches the optimum. Energy level structure analysis: The energy level diagram is used to intuitively show the relationship between the incident light depth and the energy level position, proving that the optimized perovskite thickness can achieve effective separation and transport of carriers and reduce recombination losses. Performance verification: Through finite element simulation analysis of the photocurrent characteristics of the pin structure at different voltages and comparison with the pn junction structure, the significant advantages of the pin structure in improving the photoelectric response performance are verified.

[0088] A photodetector provided in this application significantly improves the responsivity and efficiency of the photodetector through the optimized design of the thickness and energy level distribution of the perovskite absorption layer, avoiding the problems of insufficient light absorption caused by too thin a thickness or recombination losses caused by too thick a thickness.

[0089] It should be noted that in this application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation or be constructed and operated in a specific orientation.

[0090] Moreover, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0091] In addition, the terms "installed", "set up", "provided with", "connected", and "linked" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there can be internal communication between two devices, components, or parts. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0092] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, components, or parts (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, components, or parts. Unless otherwise specified, the meaning of "a plurality of" is two or more.

[0093] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A photoelectric detector, characterized in that: include: The light absorbing layer has a thickness of 500-1500 nm.

2. The photodetector according to claim 1, characterized in that: The light absorbing layer is a perovskite absorbing layer.

3. The photodetector according to claim 1, characterized in that: The thickness of the light absorbing layer is 500-1000 nm.

4. The photodetector according to claim 1, characterized in that: The thickness of the light absorbing layer is 900 nm.

5. The photodetector according to claim 2, characterized in that: The perovskite absorption layer is made of a perovskite material having a wide bandgap ABX3 structure, wherein A is an organic cation or an inorganic cation, B is a transition metal cation, and X is a halogen anion.

6. The photodetector according to claim 1, characterized in that: Also includes: A top layer is disposed on the light absorbing layer.

7. The photodetector according to claim 6, characterized in that: The top layer is a pin junction structure layer.

8. The photodetector according to claim 1, characterized in that: Also includes: An electrode is disposed on the light absorbing layer.

9. The photodetector according to claim 8, characterized in that: Also includes: A buffer layer is disposed between the electrode and the light absorbing layer.

10. The photodetector according to claim 8, characterized in that The electrode is a metal electrode or a transparent conductive oxide electrode.

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