Thin film optical voltage transformer

Abstract

Disclosed herein are systems, devices, and methods for optical voltage transformers that may have improved heat dissipation and efficiency. The optical voltage transformer may include a photovoltaic device that includes a photovoltaic layer on a semi-insulating substrate (535), wherein the photovoltaic layer comprises an array of photovoltaic cells. The semi-insulating substrate (535)may include non-conducting regions (551-554), disposed between each individual photovoltaic cell of the array of photovoltaic cells. The non-conducting regions may be voids / and or ion-implantation regions that reduce / inhibit free charge carrier mobility through the non-conduction region and between photovoltaic cells.

Description

THIN FILM OPTICAL VOLTAGE TRANSFORMERCross-Reference to Related Applications

[0001] The disclosure claims priority to US provisional application number 63 / 513,576 filed on July 14, 2023, the entire contents of which are incorporated herein by reference.Technical Field

[0002] The disclosure relates generally to optical voltage transformers, and in particular, to thin film optical voltage transformers.Background

[0003] In a wireless optical power transmission system, the basic operation involves a light-emitting device (e.g. a vertical-cavity surface-emitting laser (“VCSEL”), edge-emitting laser, light-emitting diode (“LED”), etc.) that sits in front of a light-absorbing device (e.g., a photovoltaic device or “PV”). This is generally referred to as an optical voltage transformer (“OVT”). The output power from the light-emitting device is optically transmitted to the photovoltaic device, where it is converted back to electrical power. This process may create heat. This is because a typical OVT may exhibit a power conversion efficiency of about 25 % (e.g., where the light-emitting device typically has an optical generation efficiency of 50 % and the light-absorbing device typically has a photovoltaic conversion efficiency of 50 %; thus, 50 % * 50 % = 25 %). With such a low power conversion efficiency, over 75 % of the overall input power may be in wasted as thermal energy.

[0004] This thermally wasted energy is typically dissipated through the substrate of the OVT, in either the light-emitting array (e.g., the VCSEL array) or the photovoltaic array (e.g., the PV array), which may cause a temperature gradient across the device, especially for small OVT devices, e.g., smaller than 1 mm by 1 mm in size. The heat dissipated through the substrate of the OVT may cause degradation in performance of both the light-emitting arrayand the photovoltaic array, further reducing their individual power conversion efficiencies and the overall power conversion efficiency of the OVT device.

[0005] In addition, OVTs might not have light-emitters that are perfectly aligned to their corresponding PV apertures. As a result, the emitted light may not be fully incident on the active region corresponding to the PV aperture and instead may illuminate non-active regions of the substrate. As the non-active regions of the substrate are exposed to the emitted light, the resistivity of the non-active regions may drop and it may become conductive. This may create a current leakage path through the substrate that runs underneath the PV array, shorting out the series-connected PV cells in the array that are common to the substrate. If the array is shorted, the voltage it is able to produce may be severely limited, resulting in a poor performing OVT.Brief Description of the Drawings

[0006] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the exemplary principles of the disclosure. In the following description, various exemplary aspects of the disclosure are described with reference to the following drawings, in which:FIG. 1 shows a typical optical voltage transformer (OVT) where electrical input power may be converted to output electrical power through an optical path;FIG. 2 illustrates an exemplary one-to-one OVT that includes an array of vertical-cavity surface-emitting lasers (VCSELs), each VCSEL aligned with a corresponding photovoltaic cell;FIG. 3 depicts an exemplary misalignment in a one-to-one OVT;FIGs. 4A and 4B depicts an exemplary portion of a photovoltaic (PV) array in a typical OVT with five PV cells connected in series;FIGs. 5 and 6 each depict an example of an example of a portion of a PV array that includes non-conducting regions in the PV substrate that may reduce the likelihood that a short develops in the PV substrate;FIG. 7 and 8 each show additional examples of a portion of a PV array that includes non-conducting regions in the PV substrate that may reduce the likelihood that a short develops in the PV substrate;FIG. 9 shows an example of an OVT with a PV array and a VCSEL array that have each been attached to their own non-native substrates;FIG. 10 shows an example of an OVT with a PV array and a VCSEL array that have each been attached to the same non-native substrate;FIG. 11 shows an example of possible steps in the manufacturing of a PV array and / or a VCSEL array for an OVT module, where the PV cells and / or VCSELs may be separated from one another by non-conducting regions;FIG. 12 shows an example of possible steps in the manufacturing of a PV array and / or a VCSEL array for an OVT module, where the PV cells and / or VCSELs may be separated from one another by non-conducting regions; andFIG. 13 depicts an exemplary schematic flow diagram of a method for manufacturing a PV array that may be used in an OVT module.Description

[0007] The following detailed description refers to the accompanying drawings that show, by way of illustration, exemplary details and features.

[0008] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs.

[0009] Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures, unless otherwise noted.

[0010] The phrase “at least one” and “one or more” may be understood to include a numerical quantity greater than or equal to one (e.g, one, two, three, four, [...], etc., where means that such a series may continue to any higher number). The phrase “at least one of’ with regard to a group of elements may be used herein to mean at least one element from the group consisting of the elements. For example, the phrase “at least one of’ with regard to a group of elements may be used herein to mean a selection of: one of the listed elements, a plurality of one of the listed elements, a plurality of individual listed elements, or a plurality of a multiple of individual listed elements.

[0011] The words “plural” and “multiple” in the description and in the claims expressly refer to a quantity greater than one. Accordingly, any phrases explicitly invoking the aforementioned words (e.g, “plural [elements]”, “multiple [elements]”) referring to a quantity of elements expressly refers to more than one of the said elements. For instance, the phrase “a plurality” may be understood to include a numerical quantity greater than or equal to two (e.g., two, three, four, five, [...], etc.,means that such a series may continue to any higher number).

[0012] The phrases “group (of)”, “set (of)”, “collection (of)”, “series (of)”, “sequence (of)”, “grouping (of)”, etc., in the description and in the claims, if any, refer to a quantity equal to or greater than one, i.e., one or more. The terms “proper subset”, “reduced subset”, and “lesser subset” refer to a subset of a set that is not equal to the set, illustratively, referring to a subset of a set that contains less elements than the set.

[0013] The term “semi-insulating substrate” is used herein to broadly encompass any type of material used as a substrate in a semiconductor (e.g., GaAs) which is electrically highly resistive but could be photo-sensitive (i.e., its resistivity drops with incident light on it). In general, the term “semi-insulating” is used as a prefix so that a substrate layer native to theactive device may be distinguished from a substrate layer that is not part of the active device. In this same sense, the term “non-native substrate” may used throughout to refer to a material that is not part of the active layers of a semiconducting or semi-insulating device. Ideally, the non-native substrate is non-photosensitive (e.g., it remains non-conductive even if light may be incident on it), has a high thermal conductivity (e.g., to dissipate heat), and may be exposed to high temperature processing steps. A non-native substrate may include a plastic chip carrier, a ceramic, a glass, a plastic, an aluminum nitrate, a sapphire, an epoxy, an insulator, etc.

[0014] As noted above the basic operation of an OVT involves a light-emitting device that sits in front of a light-absorbing device to transform an electrical input power into an electrical output power. FIG. 1 shows a typical OVT device (e.g., OVT 100), where electrical input power 110 may be input to a light-emitting device 115 (e.g., a VCSEL, LED, edge-emitting laser, etc.) that uses the electrical input power 110 to produce light 125 having an optical output power 120. The light 125 is directed towards a photovoltaic device 135 that receives the light 125 as optical input power 130. The photovoltaic device 135 converts the optical input power 130 into an electrical output power 140. The efficiency of the OVT 100 depends on the efficiencies of each of the light emitting device 115 and photovoltaic device 135, as well as the optical power transmission of the light 125.

[0015] FIG. 2 shows a typical OVT device (e.g., OVT device 200 that is similar to OVT 100) in more detail that includes an array of VCSELs, each VCSEL aligned with a corresponding photovoltaic cell. The VCSELs are built on a substrate 215, and in FIG. 2, two of the ten VCSELs are identified as VCSEL 218 and VCSEL 219. The photovoltaic cells (also referred to as PVs or PV cells) are built on a PV substrate 235 (also referred to as a semiinsulating substrate). Also in FIG. 2, two of the ten PV cells are identified as PV 238 and PV 239. The PV substrate 235 and VCSEL substrate 215 may be thin film substrates where the typical thickness 283 of the VCSEL substrate 215 and typical thickness 281 of the PV substrate 235 may be less than 0.2 mm. The width 282 (and / or length) of the substrate may be less than1 mm, where the array of VCSELs and PV cells may be spaced apart over the surface of the substrate by a separation of less than 0.1 mm on center (e.g., as indicated by distance 284). As should be appreciated, these dimensions are merely exemplary and any suitable dimensions may be used. As should also be appreciated, while the layer stacks depicted herein show a PV array of 10 PV cells in a line, it should be understood that the PV array may include any number of PV cells and cover an entire surface with individual PV cells in rows and / or columns that are regularly-spaced and / or irregularly spaced with respect to one another.

[0016] In the one-to-one configuration of OVT 200 shown in FIG. 2, each VCSEL in the array may be aligned to a corresponding one of the PV cells in the PV array, and the PV cells are connected in series to generate a series of voltages of each PV cell that are then additive across the array. As shown in FIG. 2, for example, VCSEL 218 is aligned to corresponding PV 238 while VCSEL 219 is aligned to corresponding PV 239, and the remaining VCSELs and PV cells have a similar one-to-one relationship. When each VCSEL is well-aligned to its corresponding PV cell, the light cone from the VCSEL (illustrated by, for example, with respect to VCSEL 218, lines 218a and 218b) is fully incident on the corresponding PV cell and provides the maximum amount of light transfer from each VCSEL to its corresponding PV cell. As should be understood, waveguides or light guides may be used to focus or direct the light from a given VCSEL to its corresponding PV cell.

[0017] As should be understood, however, the manufacturing process may introduce imperfections such that each VCSEL may not be perfectly aligned so as to transfer the maximum light to its corresponding PV cell. Instead, there may be misalignments, where the light cone is not incident only on its corresponding PV cell but also incident on a portion of the PV substrate that surrounds the PV cell. An example of misalignment is shown in FIG. 3, where OVT 300 is similar to OVT 200 of FIG. 2, except that the there is slight misalignment between a VCSEL and its corresponding PV cell. As a result of the misalignment, a portion of the cone of light from the VCSEL may be incident on portions of the PV substrate 335 near each PVcell. Not only does this reduce the light transfer from the VCSEL to its corresponding PV cell, it may also cause the PV substrate 335 itself to begin conducting, creating a short under the PV cell and therefore reducing the voltage output from the PV array. This is shown in more detail in FIGs. and 4 A and 4B.

[0018] FIG. 4A and FIG. 4B show in more detail a portion of the PV array in a typical OVT (e.g., OVT 100, 200, 300). The array shown in FIG. 4A and 4B has five PV cells (PV1, PV2, PV3, PV4, PV5) built on PV substrate 435, where the PV cells are connected in series from an anode 481 to a cathode 485 of the OVT. Each PV cell of the array may include an active stack of layers (e.g., annotated on PV1 of FIG. 4A as active stack 480) over the PV substrate 435 (e.g., n / p semiconductor layers that may include an anode layer on the PV substrate 435, followed by a p-doped layer of GaAs, followed by an n-doped layer of GaAs) with ohmic contacts (e.g., annotated on PV1 of FIG. 4A as ohmic contact 481a and ohmic contact 481b) between which a voltage is developed when light is incident on the PV cell. The ohmic contacts 481a,b may be connected in series from one PV cell to the next to form a series- connected array of PV cells from the anode 481 to the cathode 484 of the OVT. The connections between PV cells (and to the anode 481 and cathode 485 of the OVT) may be made by bonding wires or metal connects (e.g., an example of which is annotated as metal connect 477 between PV1 and PV2 on FIG. 4A).

[0019] In operation, light from the VCSEL that is incident on the PV cell causes the PV cell to develop a voltage across the corresponding PV cell (e.g., between its ohmic contacts). Ideally (e.g., when each VCSEL in the OVT is well-aligned to its corresponding PV cell such that the light cone from each VCSEL is incident only on its corresponding PV cell), the individual voltages developed by each PV cell is additive along the series connection of PV cells from anode 481 to cathode 485. Thus, as shown in FIG. 4A, for example, the total voltage ideally developed between anode 481 and cathode 485 will be VI from PV1 plus V2 from PV2 plus V3 from PV3, plus V4 from PV4, plus V5 from PV5. In a non-ideal arrangement, however,when some of the light from one or more VCSELs is incident on the PV substrate 435 (e.g., due to a misalignment, as shown in FIG. 3, where the light cone from the VCSEL is not incident only on its corresponding PV cell), the PV substrate 435 itself may become conductive. This may cause a short through the PV substrate 435, cutting off the voltage-additive effect of the series-connected PV cells. An example of this is shown in FIG. 4B, where a short 499 develops through PV substrate 435 such that the total voltage developed between anode 481 and cathode 485 may only be VI provided from PV1. As should be understood, this may cause a severe limitation to the voltage output of the PV array.

[0020] Shorting through the PV substrate may be reduced and / or eliminated, as discussed in more detail below, by building non-conducting regions in the PV substrate. Non-conducting regions may be built between each PV cell by removing portions of the PV substrate that are between PV cells (e.g., to form voids) and / or by building an ion implantation region that inhibits free charge carrier mobility between PV cells. Non-conducting regions in the PV substrate between PV cells may help reduce the likelihood that a short develops in the PV substrate, thus reducing the negative impact such a short may have on the total voltage output of the PV array.

[0021] FIGs. 5 and 6 each show an example of a portion of a PV array that includes nonconducting regions in the PV substrate to reduce the likelihood that a short develops in the PV substrate. In FIG. 5, for example, several non-conducting regions (e.g., regions 551, 552, 553, and 554) have been created in PV substrate 535 by attaching the array of PV cells to a nonnative substrate 560 and removing portions of the PV substrate 535 between PV cells (e.g., in regions 551, 552, 553, and 554) to form voids in the substrate 535. The result is that the PV substrate 535 is divided into subregions (e.g., subregions 535a, 535b, 535c, 535d, and 535e) so as to inhibit / reduce free charge carrier mobility between PV cells in the substrate subregions. Non-native substrate 560 may be a non-photosensitive substrate such that even if light may be incident on the non-native substrate 560 (e.g., due to a misaligned VCSEL), it generally remainsnon-conductive, including materials such as a ceramic material, a plastic material (e.g., a plastic-leaded chip carrier), an insulator, etc.

[0022] In FIG. 6, for example, several non-conducting regions (e.g., at regions 651, 652, 653, and 654) have been created in PV substrate 635 by forming ion implantation regions in the PV substrate 635 between PV cells (e.g., ion implantation regions 671, 672, 673, and 674). The result is that the PV substrate 635 is effectively divided into subregions (e.g., subregions 635a, 635b, 635c, 635d, and 635e) so that the substrate subregion for each individual PV cell may be separated by the ion implantation region from the substrate subregion of other PV cells. These ion implantation regions may reduce / inhibit free charge carrier mobility between PV cells and may be formed by modifying a crystalline structure of the substrate 535 material so as to reduce / inhibit free charge carrier mobility through the ion implantation region.

[0023] FIGs. 7 and 8 each show additional examples of a portion of a PV array that includes non-conducting regions in the PV substrate. In FIG. 7, the portion of the PV array is similar to that of FIG. 5, except that the non-conducting regions (e.g., regions 751, 752, 753, and 754) extend into the non-native substrate 760 such that a portion (e.g., portions 761, 762, 763, 764) of the non-native substrate 760 is removed in the non-conducting regions 751, 752, 753, and 754. In FIG. 8, the portion of the PV array is similar to that of FIG. 6 (e.g., where ion implantation regions 671, 672, 673, and 674 of FIG. 6 correspond to ion implantation regions 871, 872, 873, and 874), except that a non-native substrate 860 has been attached to the PV substrate.

[0024] The VCSEL array that may correspond to the PV array in an OVT may also have non-conducting regions between VCSELs and may be attached to non-native substrate. FIG. 9, for example, shows an OVT 900 that has a PV array (e.g., where the PV cells may be separated from one another by non-conducting regions as discussed above with respect to FIGs. 5-8) that has been attached to a PV non-native substrate 960. In OVT 900, the VCSEL array (e.g., where the VCSELs may be separated from one another by non-conducting regions) has also beenattached to a VCSEL non-native substrate 961. On the VCSEL side, the VCSEL non-native substrate 961 may serve as a heat sink to absorb heat generated by the VCSEL array.

[0025] FIG. 10, for example, shows an OVT 1000 that has a PV array (e.g., where the PV cells may be separated from one another by non-conducting regions) that has been attached to a non-native substrate 1060. In OVT 1000, the VCSEL array has also been attached to the same non-native substrate 1060, where the VCSELs may have bottom emitting apertures that emit light through the non-native substrate 1060 toward a corresponding PV cell. Having the non- native substrate 1060 be common to both the PV array and the VCSEL array may simplify the device structure and / or may reduce the size of the OVT module. Moreover, there may be no need for intermediary waveguiding optics between a VCSEL and its corresponding PV cell to guiding the light from the VCSEL to the PV cell, as the non-native substrate 1060 may serve this purpose.

[0026] FIG. 11 shows possible steps in the manufacturing of the PV array and / or a VCSEL array for an OVT module, where the PV cells and / or VCSELs may be separated from one another by non-conducting regions as discussed above with respect to FIGs. 5-8. Active layers 1180 (e.g., n / p semiconductor layers that may include an anode layer on the substrate 1135, followed by a p-doped layer of GaAs, followed by an n-doped layer of GaAs) may be grown (e.g., epitaxially) on substrate 1135 (e.g., a semiconducting / semi-insulating substrate such as GaAs) to form the PV cells on substrate 1135. As an example, active layers 1180 may have a thickness of about 10 pm grown on substrate 1160 that may be around 200 pm. Next, the substrate 1135 may be etched to a desired thickness (e.g., t about 10-15 pm). Next, the PV cells may be formed in the stack (e.g., by adding ohmic contacts, shaping, etc.) and the stack may be attached to a non-native substrate 1160. Then, non-conducting regions (e.g., at regions 1151, 1152) between PV cells may be created by etching substrate 1135 (as discussed above with respect to FIGs. 5-8) so as to segregate substrate 1135 into subregions. As noted above, the non-conducting regions may extend into the non-native substrate 1160 (e.g., regions 1171,1172). Next, metallization and / or bonding wires may be added to electrically connect the PV cells in series.

[0027] FIG. 12 shows possible steps in the manufacturing of the PV array and / or a VCSEL array for an OVT module, where the PV cells and / or VCSELs may be separated from one another by non-conducting regions as discussed above with respect to FIGs. 5-8. Active layers 1280 (e.g., n / p semiconductor layers that may include an anode layer on the substrate 1235, followed by a p-doped layer of GaAs, followed by an n-doped layer of GaAs) may be grown (e.g., epitaxially) on substrate 1235 (e.g., a semiconducting / semi-insulating substrate such as GaAs) to form the PV cells on substrate 1235, the PV cells may be shaped, and ohmic contacts may be added. Non-conducting regions (e.g., at regions 1251, 1252) may be created by removing a portion of the substrate 1235 (e.g., 2-3 pm from the top of substrate 1235) and using ion implantation (e.g., to a depth of about 10 pm) as discussed above with respect to FIGs. 5-8. Next, metallization may be added to electrically connect the PV cells in series and the substrate 1235 may be bottom-etched / ground to a desired thickness (e.g., etched back to the ionimplantation region) so as to effectively segregate substrate 1235 into subregions (e.g., subregions 1235a, 1235b, 1235c) with ion implantation regions in between (e.g., ion implantation regions 1271, 1272). The ion implantation regions 1271, 1272 help to keep the resistivity of the material high between subregions of the substrate 1235, so that even if light is incident on these regions and the substrate 1235 were to show a photo-sensitive response, the higher resistivity reduces / prevents shorting between PV cells. As noted above, a non-native substrate 1260 may be attached.

[0028] FIG. 13 depicts a schematic flow diagram of a method 1300 for forming a PV array that may be used in an OVT. Method 1300 may implement any of the features discussed above with respect to the features of the OVTs, PV arrays, VCSEL arrays, and any of FIGs. 1-12 discussed above. Method 1300 includes, in 1310, disposing a photovoltaic layer on a (e.g., semi-insulating) substrate, wherein the photovoltaic layer comprises an array of photovoltaiccells. Method 1300 includes, in 1320, modifying regions of the (e.g., semi-insulating) substrate disposed between each photovoltaic cell of the array of photovoltaic cells to form nonconducting regions in the semi-insulating substrate.

[0029] In the following, various examples are provided that may include one or more aspects described above with reference to the features of the OVTs, PV arrays, VCSEL arrays, and any of FIGs. 1-12 discussed above. The examples provided in relation to the devices may apply also to the described method(s), and vice versa.

[0030] Example 1 is method for fabricating a photovoltaic device, the method including disposing a photovoltaic layer on a (e.g., semi-insulating) substrate, wherein the photovoltaic layer includes an array of photovoltaic cells. The method also includes modifying regions of the semi-insulating substrate disposed between each photovoltaic cell of the array of photovoltaic cells to form non-conducting regions in the semi-insulating substrate.

[0031] Example 2 is the method of example 1, wherein the modifying the regions to form the non-conducting regions includes (1) etching the regions to form voids in the in the semiinsulating substrate, wherein the non-conducting regions include the voids or (2) implanting ions in the regions to form ion-implant regions in the semi-insulating substrate, wherein the non-conducting regions include the ion-implant regions.

[0032] Example 3 is the method of either of examples 1 or 2, wherein the non-conducting regions extend completely through a layer thickness of the semi-insulating substrate.

[0033] Example 4 is the method of any of examples 1 to 3, the method further including attaching the semi-insulating substrate to a non-native substrate.

[0034] Example 5 is the method of example 4, wherein the non-conducting regions extend at least partially into the non-native substrate.

[0035] Example 6 is the method of either of examples 4 or 5, wherein the non-native substrate is a non-photosensitive material.

[0036] Example 7 is the method of any of examples 4 to 6, wherein the non-native substrate includes a ceramic material, a plastic material (e.g., a plastic-leaded chip carrier), or an insulator.

[0037] Example 8 is the method of any of examples 4 to 7, wherein the non-native substrate includes aluminum nitrate or sapphire.

[0038] Example 9 is the method of any of examples 2 to 8, wherein the implanting the ions in the regions to form the non-conducting regions includes modifying a crystalline structure in the regions to inhibit free charge carrier mobility through the regions.

[0039] Example 10 is the method of any of examples 1 to 9, wherein the disposing the photovoltaic layer on the semi-insulating substrate includes growing a plurality of layers with epitaxial growth to form the array of photovoltaic cells.

[0040] Example 11 is the method of any of examples 1 to 10, the method further including bonding the array of photovoltaic cells to one another in series (e.g., via a metallization or bonding wires).

[0041] Example 12 is the method of any of examples 1 to 11, the method further packaging the photovoltaic device with an array of vertical-cavity surface-emitting laser (VCSEL) devices that correspond to the array of photovoltaic cells to form an optical voltage transformer, wherein a direction of light output of each VCSEL device of the array of VCSEL devices is toward a corresponding one of the array of photovoltaic cells.

[0042] Example 13 is the method of any of examples 1 to 12, the method further including attaching the semi-insulating substrate to a non-native substrate. The method also includes attaching the array of VCSEL devices to a non-native substrate that is different from the non- native substrate.

[0043] Example 14 is the method of any of examples 1 to 13, the method further including attaching the semi-insulating substrate to a non-native substrate. The method also includesattaching the array of VCSEL devices to the non-native substrate, wherein the non-native substrate is disposed between the array of VCSEL devices and the array of photovoltaic cells.

[0044] Example 15 is a device including an array of photovoltaic cells connected in series and located on a semi-insulating substrate non-conducting regions disposed within the semiinsulating substrate and arranged between each photovoltaic cell of the array of photovoltaic cells.

[0045] Example 16 is the device of example 15, wherein the non-conducting regions include (1) voids that extend through the semi-insulating substrate or (2) ion-implant regions that extend through the semi-insulating substrate.

[0046] Example 17 is the device of either of examples 15 or 16, wherein the nonconducting regions (e.g., the voids or the ion-implant regions) extend completely through a layer thickness of the semi-insulating substrate.

[0047] Example 18 is the device of any of examples 15 to 17, the device further including a non-native substrate attached to the semi-insulating substrate.

[0048] Example 19 is the device of example 18, wherein the non-conducting regions extend at least partially into the non-native substrate.

[0049] Example 20 is the device of either of examples 18 or 19, wherein the non-native substrate is a non-photosensitive material.

[0050] Example 21 is the device of any of examples 18 to 20, wherein the non-native substrate includes a ceramic material, a plastic material, or an insulator.

[0051] Example 22 is the device of any of examples 18 to 21, wherein the non-native substrate includes aluminum nitrate or sapphire.

[0052] Example 23 is the device of any of examples 16 to 22, wherein the ion implant regions have a crystallin structure that inhibits free charge carrier mobility as compared to other regions of the semi-insulating substrate.

[0053] Example 24 is the device of any of examples 15 to 23, the device further including metal interconnects (e.g. bonding wires) that connect the array of photovoltaic cells in series.

[0054] Example 25 is the device of any of examples 15 to 24, the device further including an array of vertical-cavity surface-emitting laser (VCSEL) devices, each of which corresponds to a corresponding one cell of the array of photovoltaic cells to form an optical voltage transformer, wherein each VCSEL device of the array of VCSEL devices is configured to emit light in a direction toward a corresponding one of the array of photovoltaic cells.

[0055] Example 26 is the device of any of examples 15 to 25, the device further including a non-native substrate attached to the semi-insulating substrate and an other non-native substrate attached to the array of VCSEL devices that is different from the non-native substrate.

[0056] Example 27 is the device of any of examples 15 to 26, the device further including a non-native substrate attached to the semi-insulating substrate and the array of VCSEL devices, wherein the non-native substrate is disposed between the array of VCSEL devices and the array of photovoltaic cells, wherein the array of VCSEL devices is configured to emit light toward the array of photovoltaic cells through the non-native substrate.

[0057] Example 28 is an optical voltage transformer including a photovoltaic system that includes an array of photovoltaic cells connected in series and located on a semi-insulating substrate and on-conducting regions disposed within the semi-insulating substrate and arranged between each individual photovoltaic cell of the array of photovoltaic cells. The optical voltage transformer further includes a vertical -cavity surface-emitting laser (VCSEL) system that includes an array of vertical-cavity surface-emitting laser (VCSEL) device. Each VCSEL device of the array corresponds to one of the array of photovoltaic cells, wherein each VCSEL device of the array of VCSEL devices is configured to emit light in a direction toward a corresponding one of the array of photovoltaic cells.

[0058] Example 29 is the optical voltage transformer of example 28, the optical voltage transformer further including a non-native substrate attached to the semi-insulating substrate.The optical voltage transformer also includes another non-native substrate attached to the array of VCSEL devices that is different from the non-native substrate.

[0059] Example 30 is the optical voltage transformer of either of examples 28 or 29, the optical voltage transformer further including a non-native substrate attached to the semiinsulating substrate and the array of VCSEL devices, wherein the non-native substrate is disposed between the array of VCSEL devices and the array of photovoltaic cells, wherein the array of VCSEL devices is configured to emit light toward the array of photovoltaic cells through the non-native substrate.

[0060] While the disclosure has been particularly shown and described with reference to specific aspects, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims. The scope of the disclosure is thus indicated by the appended claims and all changes, which come within the meaning and range of equivalency of the claims, are therefore intended to be embraced.

Claims

CLAIMSClaimed is:

1. A method for fabricating a photovoltaic device, the method comprising: disposing a photovoltaic layer on a substrate, wherein the photovoltaic layer comprises an array of photovoltaic cells; and modifying regions of the substrate disposed between each individual photovoltaic cell of the array of photovoltaic cells to form non-conducting regions in the substrate.

2. The method of claim 1, wherein the modifying the regions to form the non-conducting regions comprises: etching the regions to form voids in the substrate, wherein the non-conducting regions comprise the voids; or implanting ions in the regions to form ion-implant regions in the substrate, wherein the non-conducting regions comprise the ion-implant regions.

3. The method of either of claims 1 or 2, wherein the non-conducting regions extend completely through a layer thickness of the substrate.

4. The method of any of claims 1 to 3, the method further comprising attaching the substrate to a non-native substrate.

5. The method of claim 4, wherein the non-conducting regions extend at least partially into the non-native substrate.

6. The method of either of claims 4 or 5, wherein the non-native substrate is a nonphotosensitive material.

7. The method of any of claims 4 to 6, wherein the non-native substrate comprises a ceramic material, a plastic material (e.g., a plastic-leaded chip carrier), or an insulator.

8. The method of any of claims 4 to 7, wherein the non-native substrate comprises aluminum nitrate or sapphire.

9. The method of any of claims 2 to 8, wherein the implanting the ions in the regions to form the non-conducting regions comprises modifying a crystalline structure in the regions to inhibit free charge carrier mobility through the regions.

10. The method of any of claims 1 to 9, wherein the disposing the photovoltaic layer on the substrate comprises growing a plurality of layers with epitaxial growth to form the array of photovoltaic cells.

11. The method of any of claims 1 to 10, the method further comprising bonding the array of photovoltaic cells to one another in series.

12. The method of any of claims 1 to 11, the method further packaging the photovoltaic device with an array of vertical-cavity surface-emitting laser (VCSEL) devices that correspond to the array of photovoltaic cells to form an optical voltage transformer, wherein a direction of light output of each VCSEL device of the array of VCSEL devices is toward a corresponding one of the array of photovoltaic cells.

13. The method of any of claims 1 to 12, the method further comprising: attaching the substrate to a non-native substrate; and attaching the array of VCSEL devices to a non-native substrate that is different from the non-native substrate.

14. The method of any of claims 1 to 13, the method further comprising: attaching the substrate to a non-native substrate; andattaching the array of VCSEL devices to the non-native substrate, wherein the nonnative substrate is disposed between the array of VCSEL devices and the array of photovoltaic cells.

15. A device comprising: an array of photovoltaic cells connected in series and located on a substrate; and non-conducting regions disposed within the substrate and arranged between each photovoltaic cell of the array of photovoltaic cells.

16. The device of claim 15, wherein the non-conducting regions comprise: voids that extend through the substrate; or ion-implant regions that extend through the substrate.

17. The device of either of claims 15 or 16, wherein the non-conducting regions (e.g., the voids or the ion-implant regions) extend completely through a layer thickness of the substrate.

18. The device of any of claims 15 to 17, the device further comprising a non-native substrate attached to the substrate.

19. The device of claim 18, wherein the non-conducting regions extend at least partially into the non-native substrate.

20. The device of either of claims 18 or 19, wherein the non-native substrate is a nonphotosensitive material.

21. The device of any of claims 18 to 20, wherein the non-native substrate comprises a ceramic material, a plastic material, or an insulator.

22. The device of any of claims 18 to 21, wherein the non-native substrate comprises aluminum nitrate or sapphire.

23. The device of any of claims 16 to 22, wherein the ion implant regions have a crystallin structure that inhibits free charge carrier mobility as compared to other regions of the substrate.

24. The device of any of claims 15 to 23, the device further including metal connects (e.g. bonding wires) that connect the array of photovoltaic cells in series.

25. The device of any of claims 15 to 24, the device further comprising an array of verticalcavity surface-emitting laser (VCSEL) devices, each of which corresponds to a corresponding one cell of the array of photovoltaic cells to form an optical voltage transformer, wherein each VCSEL device of the array of VCSEL devices is configured to emit light in a direction toward a corresponding one of the array of photovoltaic cells.

26. The device of any of claims 15 to 25, the device further comprising: a non-native substrate attached to the substrate; and an other non-native substrate attached to the array of VCSEL devices that is different from the non-native substrate.

27. The device of any of claims 15 to 26, the device further comprising a non-native substrate attached to the substrate and the array of VCSEL devices, wherein the non-native substrate is disposed between the array of VCSEL devices and the array of photovoltaic cells, wherein the array of VCSEL devices is configured to emit light toward the array of photovoltaic cells through the non-native substrate.

28. An optical voltage transformer comprising: a photovoltaic system comprising: an array of photovoltaic cells connected in series and located on a substrate; andnon-conducting regions disposed within the substrate and arranged between each individual photovoltaic cell of the array of photovoltaic cells; and a vertical-cavity surface-emitting laser (VCSEL) system comprising an array of vertical-cavity surface-emitting laser (VCSEL) devices, each corresponding to one of the array of photovoltaic cells, wherein each VCSEL device of the array of VCSEL devices is configured to emit light in a direction toward a corresponding one of the array of photovoltaic cells.

29. The optical voltage transformer of claim 28, the optical voltage transformer further comprising: a non-native substrate attached to the substrate; and an other non-native substrate attached to the array of VCSEL devices that is different from the non-native substrate.

30. The optical voltage transformer of either of claims 28 or 29, the optical voltage transformer further comprising a non-native substrate attached to the substrate and the array of VCSEL devices, wherein the non-native substrate is disposed between the array of VCSEL devices and the array of photovoltaic cells, wherein the array of VCSEL devices is configured to emit light toward the array of photovoltaic cells through the non-native substrate.

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