# US 2013/0153013 A1 · Photovoltaic device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0153013 A1 - Document ID: US20130153013A1 - Status: Published application - Kind: A1 - Application number: 13/772,043 - Filed: 2013-02-20 - Published: 2013-06-20 - Earliest claimed: 2008-10-23 - Assignees: Alta Devices, Inc. - Inventors: Melissa J. ARCHER; Thomas J. GMITTER; Gang HE; Gregg HIGASHI - Web page: https://patentgrep.com/patent/US20130153013A1 ## CPC - H10F 77/124: comprising only Group III-V materials, e.g. GaAs - H10F 10/13: Photovoltaic cells having absorbing layers comprising graded bandgaps - H10F 10/144: comprising only Group III-V materials, e.g. GaAs,AlGaAs, or InP photovoltaic cells - H10F 10/146: {Back-junction photovoltaic cells, e.g. having interdigitated base-emitter regions on the back side} - H10F 10/163: comprising only Group III-V materials, e.g. GaAs/AlGaAs or InP/GaInAs photovoltaic cells - H10F 77/1248: {having three or more elements, e.g. GaAlAs, InGaAs or InGaAsP} - H10F 77/219: {Arrangements for electrodes of back-contact photovoltaic cells} - H10F 77/48: Back surface reflectors [BSR] - H10F 77/70: Surface textures, e.g. pyramid structures - H10F 77/703: {of the semiconductor bodies, e.g. textured active layers} - Y02E 10/50: Photovoltaic [PV] energy - Y02E 10/52: PV systems with concentrators - Y02E 10/544: Solar cells from Group III-V materials - Y02E 10/547: Monocrystalline silicon PV cells - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract Methods and apparatus are provided for converting electromagnetic radiation, such as solar energy, into electric energy with increased efficiency when compared to conventional solar cells. One embodiment of the present invention provides a photovoltaic (PV) device. The PV device comprises an absorber layer made of a compound semiconductor; and an emitter layer located closer than the absorber layer to a first side of the device. The PV device includes a p-n junction formed between the emitter layer and the absorber layer, the p-n junction causing a voltage to be generated in the device in response to the device being exposed to light at a second side of the device. Such innovations may allow for greater efficiency and flexibility in PV devices when compared to conventional solar cells. ## Claims ### Claim 1 A photovoltaic (PV) device comprising: an absorber layer made of a compound semiconductor; an emitter layer located closer than the absorber layer to a first side of the device; and a p-n junction formed between the emitter layer and the absorber layer, the p-n junction causing a voltage to be generated in the device in response to the device being exposed to light at a second side of the device. ### Claim 2 (depends on 1) The photovoltaic (PV) device of claim 1 wherein the first side of the device is a back side of the device and the second side of the device is a front side of the device. ### Claim 3 (depends on 1) The photovoltaic (PV) device of claim 1 wherein the emitter layer is made of a different material than the absorber layer, such that a heterojunction is formed between the emitter layer and the absorber layer. ### Claim 4 (depends on 3) The photovoltaic (PV) device of claim 3 wherein the emitter layer has a larger bandgap than the absorber layer. ### Claim 5 (depends on 3) The photovoltaic (PV) device of claim 3 wherein an intermediate layer or layers is located between the absorber layer and the emitter layer. ### Claim 6 (depends on 5) The photovoltaic (PV) device of claim 5 wherein the intermediate layer or layers provides an offset between the p-n junction and the semiconductor heterojunction. ### Claim 7 (depends on 5) The photovoltaic (PV) device of claim 5 wherein the intermediate layer includes a graded layer that varies from the composition of the material of the absorber layer to the composition of the material of the emitter layer. ### Claim 8 (depends on 1) The photovoltaic (PV) device of claim 1 wherein recesses are formed through the emitter layer and partly through the absorber layer, allowing for electrical contact to both the emitter and absorber layers from the same side of the device. ### Claim 9 (depends on 1) The photovoltaic (PV) device of claim 1 wherein the material of the absorber layer is a III-V semiconductor. ### Claim 10 (depends on 9) The photovoltaic (PV) device of claim 9 wherein the material of the absorber layer is gallium arsenide (GaAs). ### Claim 11 (depends on 9) The photovoltaic (PV) device of claim 9 wherein the material of the absorber layer is indium gallium phosphide (InGaP). ### Claim 12 (depends on 1) The photovoltaic (PV) device of claim 1 wherein the material of the emitter layer is a III-V semiconductor. ### Claim 13 (depends on 12) The photovoltaic (PV) device of claim 12 wherein the material of the emitter layer is aluminum gallium arsenide (AlGaAs). ### Claim 14 (depends on 12) The photovoltaic (PV) device of claim 12 wherein the material of the emitter layer is aluminum gallium indium phosphide (AlGaInP). ### Claim 15 (depends on 1) The photovoltaic (PV) device of claim 1 wherein the material of the absorber layer is an n-type semiconductor. ### Claim 16 (depends on 1) The photovoltaic (PV) device of claim 1 wherein the material of the emitter layer is a p-type semiconductor. ### Claim 17 (depends on 5) The photovoltaic (PV) device of claim 5 wherein the intermediate layer or layers include one or more n-type semiconductor. ### Claim 18 (depends on 5) The photovoltaic (PV) device of claim 5 wherein the intermediate layer or layers include one or more intrinsic semiconductor. ### Claim 19 (depends on 5) The photovoltaic (PV) device of claim 5 wherein the intermediate layer or layers include one or more compensated semiconductor. ### Claim 20 (depends on 1) The photovoltaic (PV) device of claim 1 further including a reflector layer, wherein the emitter layer is located between the absorber layer and the reflector layer. ### Claim 21 (depends on 20) The photovoltaic (PV) device of claim 20 wherein the reflector layer is metallic. ### Claim 22 (depends on 20) The photovoltaic (PV) device of claim 20 wherein the reflector also provides electrical connection to the device. ### Claim 23 (depends on 20) The photovoltaic (PV) device of claim 20 wherein a dielectric layer is located between the emitter layer and the reflector layer. ### Claim 24 (depends on 20) The photovoltaic (PV) device of claim 20 further including a diffuser layer located between the absorber layer and the first side of the device, wherein the diffuser layer scatters light at multiple angles for improved light trapping.