# US 2014/0196780 A1 · Photovoltaic devices with an interfacial band-gap modifying structure and methods for forming the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0196780 A1 - Document ID: US20140196780A1 - Status: Published application - Kind: A1 - Application number: 14/218,410 - Filed: 2014-03-18 - Published: 2014-07-17 - Earliest claimed: 2010-08-04 - Assignees: Egypt Nanotechnology Center; International Business Machines Corporation - Applicants: Egypt Nanotechnology Center; International Business Machines Corporation - Inventors: Keith E. Fogel; Jeehwan Kim; Devendra K. Sadana; George S. Tulevski; Ahmed Abou-Kandil; Hisham S. Mohamed; Mohamed Saad; Osama Tobail - Web page: https://patentgrep.com/patent/US20140196780A1 ## CPC - H10F 71/138: {Manufacture of transparent electrodes, e.g. transparent conductive oxides [TCO] or indium tin oxide [ITO] electrodes} - H10F 10/17: Photovoltaic cells having only PIN junction potential barriers - H10F 10/18: Photovoltaic cells having only Schottky potential barriers - H10F 71/1035: {having multiple Group IV elements, e.g. SiGe or SiC} - H10F 77/122: comprising only Group IV materials - H10F 77/244: {made of transparent conductive layers, e.g. transparent conductive oxide [TCO] layers} - H10F 77/251: {comprising zinc oxide [ZnO]} - H10F 77/413: {directly associated or integrated with the devices, e.g. back reflectors (directly associated or integrated with photovoltaic cells H10F77/42)} - H10F 77/48: Back surface reflectors [BSR] - Y02E 10/52: PV systems with concentrators - Y02E 10/547: Monocrystalline silicon PV cells - Y02E 10/548: Amorphous 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 A Schottky-barrier-reducing layer is provided between a p-doped semiconductor layer and a transparent conductive material layer of a photovoltaic device. The Schottky-barrier-reducing layer can be a conductive material layer having a work function that is greater than the work function of the transparent conductive material layer. The conductive material layer can be a carbon-material layer such as a carbon nanotube layer or a graphene layer. Alternately, the conductive material layer can be another transparent conductive material layer having a greater work function than the transparent conductive material layer. The reduction of the Schottky barrier reduces the contact resistance across the transparent material layer and the p-doped semiconductor layer, thereby reducing the series resistance and increasing the efficiency of the photovoltaic device. ## Claims ### Claim 1 A photovoltaic device comprising a stack, from one side to another side, of a transparent conductive material layer, a Schottky-barrier-reducing layer contacting said transparent conductive material layer, and a p-doped semiconductor layer, wherein a Schottky barrier across said stack has a lower contact resistance than a Schottky barrier across a comparative exemplary stack that includes all layers of said stack less said Schottky-barrier-reducing layer, wherein said Schottky-barrier-reducing layer is an optically transparent layer including an allotrope of carbon and is in direct contact with said p-doped semiconductor layer and is in direct contact with said transparent conductive material layer, wherein said Schottky-barrier-reducing layer includes a same material as said transparent conductive material layer and has a different doping than said transparent conductive material layer. ### Claim 2 (depends on 1) The photovoltaic device of claim 1, wherein said transparent conductive material layer includes an aluminum-doped zinc oxide having an aluminum doping at a first dopant concentration, and said Schottky-barrier-reducing layer includes an aluminum-doped zinc oxide having an aluminum doping at a second dopant concentration, wherein said first dopant concentration is greater than said second dopant concentration. ### Claim 3 (depends on 1) The photovoltaic device of claim 1, wherein said transparent conductive material layer includes a first fluorine-doped tin oxide having a fluorine doping at a first dopant concentration, and said Schottky-barrier-reducing layer includes a second fluorine-doped tin oxide having a fluorine doping at a second dopant concentration, wherein said first dopant concentration is greater than said second dopant concentration. ### Claim 4 (depends on 1) The photovoltaic device of claim 1, wherein said Schottky-barrier-reducing layer includes a material having a higher resistivity than a material of said transparent conductive material layer. ### Claim 5 (depends on 1) The photovoltaic device of claim 1, wherein said Schottly-barrier-reducing layer has a work function that is greater than a work function of said transparent conductive material layer and is lesser than an absolute value of a Fermi level of said p-doped semiconductor layer. ### Claim 6 (depends on 1) The photovoltaic device of claim 1, wherein a series resistance of said photovoltaic device is equal to or less than 9 Ohms-cm2. ### Claim 7 (depends on 1) The photovoltaic device of claim 1, wherein said p-doped semiconductor layer includes a hydrogenated p-doped semiconductor-containing material. ### Claim 8 (depends on 1) The photovoltaic device of claim 1, further comprising: an intrinsic semiconductor layer contacting said p-doped semiconductor layer; and an n-doped semiconductor layer contacting said intrinsic semiconductor layer. ### Claim 9 (depends on 8) The photovoltaic device of claim 8, wherein said intrinsic semiconductor layer includes a hydrogenated amorphous intrinsic semiconductor material. ### Claim 10 (depends on 8) The photovoltaic device of claim 8, wherein said n-doped semiconductor layer includes hydrogenated n-doped amorphous semiconductor material. ### Claim 11 (depends on 8) The photovoltaic device of claim 8, further comprising at least one back reflector layer located on said n-doped semiconductor layer. ### Claim 12 A method of forming a photovoltaic device comprising: forming a transparent conductive material layer on a substrate; forming a Schottky-barrier-reducing layer on said transparent conductive material layer, wherein said Schottky-barrier-reducing layer includes a same material as said transparent conductive material layer and has a different doping than said transparent conductive material layer; and forming a p-doped semiconductor layer on said Schottky-barrier-reducing layer, wherein a Schottky barrier across a stack of said transparent conductive material layer, said Schottky-barrier-reducing layer, and said p-doped semiconductor layer has less contact resistance than a Schottky barrier across another stack that includes all layers of said stack less said Schottky-barrier-reducing layer. ### Claim 13 (depends on 12) The method of claim 12, wherein said transparent conductive material layer includes an aluminum-doped zinc oxide having an aluminum doping at a first dopant concentration, and said Schottky-barrier-reducing layer includes an aluminum-doped zinc oxide having an aluminum doping at a second dopant concentration, wherein said first dopant concentration is greater than said second dopant concentration. ### Claim 14 (depends on 12) The method of claim 12, wherein said transparent conductive material layer includes a first fluorine-doped tin oxide having a fluorine doping at a first dopant concentration, and said Schottky-barrier-reducing layer includes a second fluorine-doped tin oxide having a fluorine doping at a second dopant concentration, wherein said first dopant concentration is greater than said second dopant concentration. ### Claim 15 (depends on 12) The method of claim 12, wherein said Schottky-barrier-reducing layer includes a material having a higher resistivity than a material of said transparent conductive material layer. ### Claim 16 (depends on 12) The method of claim 12, wherein said Schottky-barrier-reducing layer has a work function that is greater than a work function of said transparent conductive material layer and is lesser than an absolute value of a Fermi level energy of said p-doped semiconductor layer. ### Claim 17 (depends on 12) The method of claim 12, further comprising: forming an intrinsic semiconductor layer on said p-doped semiconductor layer; and forming an n-doped semiconductor layer on said intrinsic semiconductor layer. ### Claim 18 (depends on 17) The method of claim 17, wherein said intrinsic semiconductor layer includes a hydrogenated amorphous intrinsic semiconductor material. ### Claim 19 (depends on 17) The method of claim 17, wherein said n-doped semiconductor layer includes hydrogenated n-doped amorphous semiconductor material. ### Claim 20 (depends on 17) The method of claim 17, further comprising forming at least one back reflector layer on said n-doped semiconductor layer.