# US 11,908,963 B2 · Photovoltaic device with band-stop filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,908,963 B2 - Document ID: US11908963B2 - Status: Granted - Kind: B2 - Application number: 13/900,588 - Filed: 2013-05-23 - Published: 2013-11-28 - Granted: 2024-02-20 - Earliest claimed: 2012-05-24 - Assignees: Internationa Business Machines Corporation; Egypt Nanotechnology Center - Applicants: International Business Machines Corporation; Egypt Nanotechnology Center - Inventors: Wanda Andreoni; Alessandro Curioni; Petr Khomyakov; Jeehwan Kim; Devendra K. Sadana; Nasser D. Afify - Web page: https://patentgrep.com/patent/US11908963B2 ## CPC - H10F 77/166: Amorphous semiconductors - H10F 77/315: {the coatings being antireflective or having enhancing optical properties} - H10F 77/337: {using interference filters, e.g. multilayer dielectric filters} - Y02E 10/52: PV systems with concentrators - 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 Photovoltaic device with band-stop filter. The photovoltaic device includes an amorphous photovoltaic material and a band-stop filter structure having a stopband extending from a lower limiting angular frequency ωmin≥0 to an upper limiting angular frequency ωmax where ωmax>ωmin. The band-stop filter structure is arranged in the photovoltaic device relative to the photovoltaic material in order to attenuate electromagnetic radiations reaching the photovoltaic material with angular frequencies of ω* in the stopband, so that ωmin<ω*<ωmax. The angular frequencies ω* correspond to electronic excitations ℏω* from valence band tail (VBT) states of the amorphous photovoltaic material to conduction band tail (CBT) states of the amorphous photovoltaic material. ## Claims ### Claim 1 A photovoltaic device, comprising: an active photovoltaic device region comprising alternating layers of different amorphous photovoltaic materials, a first band-stop filter structure on the active photovoltaic device region; an intermediate photovoltaic layer on the first band-stop filter structure; a second band-stop filter structure on the first band-stop filter structure intermediate photovoltaic layer such that the intermediate photovoltaic layer is interposed between the first and second first and second band-stop filter structures, wherein each of the first and second band-stop filter structures comprise: alternating layers of dielectric materials having a stopband extending from a lower limiting angular frequency ωmin≥0 to an upper limiting angular frequency ωmax, wherein ωmax>ωmin, the first band-stop filter structure on the active photovoltaic device region such that the alternating layers of different amorphous photovoltaic materials are arranged completely beneath the first and second band-stop filter structures and such that the at least one of the first and second band-stop filter structure is arranged in the photovoltaic device relative to the alternating layers of different amorphous photovoltaic materials in order to block electromagnetic radiations reaching portions of the alternating layers of different amorphous photovoltaic materials with angular frequencies of ω* in the stopband, so that ωmin<ω*<ωmax; wherein said angular frequencies ω* correspond to blocked electronic excitations ℏω* from valence band tail (VBT) states of each amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials to conduction band tail (CBT) states of each amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials; wherein the angular frequencies of the blocked electromagnetic radiations are the same as the angular frequencies that correspond to the blocked electronic excitations; wherein light at angular frequencies ω* cause light-induced degradation of the photovoltaic device, wherein ωmax is based on an Urbach energy component EUC of a conduction band tail region, wherein ωmin is based on an Urbach energy component EUV of a valence band tail region, and wherein the photovoltaic device permits electromagnetic radiations reaching portions of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials with angular frequencies of ω* in the stopband, where the electromagnetic radiations have angular frequencies that are >ωmax or <ωmin. ### Claim 2 (depends on 1) The photovoltaic device according to claim 1, wherein an energy ℏωmax corresponding to an upper limiting angular frequency ωmax of the stopband is less than a mobility gap ℏωM of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials. ### Claim 3 (depends on 1) The photovoltaic device according to claim 1, wherein an energy ℏωmax corresponding to an upper limiting angular frequency ωmax of the stopband is equal to a mobility gap ℏωM of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials. ### Claim 4 (depends on 1) The photovoltaic device according to claim 1, wherein an energy ℏωmin corresponding to the lower limiting angular frequency of the stopband is less than an optical gap ℏωgap of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials. ### Claim 5 (depends on 1) The photovoltaic device according to claim 1, wherein an energy comprising 2ℏ(Δωc+Δωv) and corresponding to a width of the stopband of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials is twice the sum of: a first energy change ℏΔωc that corresponds to the extent of the conduction band tail region of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials; and a second energy change ℏΔωv that corresponds to the extent of the valence band tail region of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials. ### Claim 6 (depends on 5) The photovoltaic device according to claim 5, wherein a frequency corresponding to a gap energy ωgap corresponds to an optical gap energy ℏωgap of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials. ### Claim 7 (depends on 5) The photovoltaic device according to claim 5, wherein a change in frequency corresponding to a first energy Δωc and a change in frequency corresponding to a second energy Δωv correspond to the first energy change ℏΔωc and the second energy change ℏΔωv respectively, and correspond to the extent of the conduction band tail region of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials and the extent of the valence band tail region of a given amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials, respectively. ### Claim 8 (depends on 1) The photovoltaic device according to claim 1, wherein the alternating layers of different amorphous photovoltaic materials comprises hydrogenated amorphous silicon (a-SI:H) and hydrogenated amorphous silicon doped with germanium (a-Si1-xGex:H). ### Claim 9 (depends on 5) The photovoltaic device according to claim 5, wherein at least one of the alternating layers comprises hydrogenated amorphous silicon wherein a gap energy ℏωgap is between 1.7 and 2.0 eV and a sum of the first energy change and the second energy change ℏΔωc+ℏΔωv is less than 0.2 eV. ### Claim 10 (depends on 5) The photovoltaic device according to claim 5, wherein at least one amorphous photovoltaic material included in the alternating layers of amorphous photovoltaic materials comprises hydrogenated amorphous silicon wherein a gap energy ℏωgap is between 1.7 and 2.0 eV and a sum of the first energy change and the second energy change ℏΔωc+ℏΔωv is between 0.1 eV and 0.2 eV. ### Claim 11 (depends on 1) The photovoltaic device according to claim 1, wherein the amorphous photovoltaic material comprises at least one of the following: hydrogenated amorphous silicon doped with germanium (a-Si1-xGex:H) or doped with germanium and carbon (a-Si1-x-yGexCy:H); an inorganic amorphous material; and an organic photovoltaic material. ### Claim 12 (depends on 1) The photovoltaic device according to claim 1, wherein the photovoltaic device has a layer structure, wherein one or more layers of said layer structure forms at least one of the first and second band-stop filter structures. ### Claim 13 (depends on 10) The photovoltaic device according to claim 10, wherein a layer structure of the photovoltaic device comprises a pattern of two or more contiguous layers of different materials and the pattern is repeated along the layer structure. ### Claim 14 (depends on 13) The photovoltaic device according to claim 13, wherein at least one layer of amorphous photovoltaic material included in the alternating layers of different amorphous photovoltaic materials is designed to absorb radiation frequencies within the stopband. ### Claim 15 (depends on 10) The photovoltaic device according to claim 10, wherein the alternating layers of different amorphous photovoltaic materials forms a Bragg reflector configured to reflect radiations with frequencies within the stopband. ### Claim 16 (depends on 10) The photovoltaic device according to claim 10, wherein the first band-stop filter structure is a band-stop filter layer contiguous with one layer of a the alternating layers of different amorphous photovoltaic materials. ### Claim 17 (depends on 1) The photovoltaic device according to claim 1, wherein the intermediate photovoltaic layer is formed from a semiconductor material.