# US 12,765,115 B2 · Bifacial enhancement layers and photovoltaic devices including the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,765,115 B2 - Document ID: US12765115B2 - Status: Granted - Kind: B2 - Application number: 18/703,192 - Filed: 2022-10-26 - Published: 2024-12-12 - Granted: 2026-10-13 - Earliest claimed: 2021-10-26 - Assignees: First Solar, Inc. - Applicants: First Solar, Inc. - Inventors: James Becker; William Huber; Chungho Lee; Jialiu Ma; Dirk Weiss; Gang Xiong - Web page: https://patentgrep.com/patent/US12765115B2 ## CPC - H10F 77/315: {the coatings being antireflective or having enhancing optical properties} - H10F 77/45: Wavelength conversion means, e.g. by using luminescent material, fluorescent concentrators or up-conversion arrangements - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION ## Abstract Photovoltaic devices having bifacial enhancement are described herein. ## Claims ### Claim 1 A bifacial photovoltaic device comprising: an absorber layer having a front interface and a back interface, wherein the front interface has a front average quantum efficiency to light between 500 nm and 900 nm and the back interface has a back average quantum efficiency to light between 500 nm and 900 nm, and wherein the back average quantum efficiency is less than or equal to 50% of the front average quantum efficiency and greater than or equal to 5% of the front average quantum efficiency; and a bifacial enhancement layer over the absorber layer and positioned closer to the back interface of the absorber layer compared to the front interface of the absorber layer, wherein: the bifacial enhancement layer absorbs light having an absorbed wavelength less than or equal to a cutoff wavelength of an absorption edge of the bifacial enhancement layer; the cutoff wavelength corresponds to an absorbance equal to 15% of a maximum absorbance of the bifacial enhancement layer; the bifacial enhancement layer emits an emitted photoluminescence having a peak; a wavelength of the peak of the emitted photoluminescence of the bifacial enhancement layer is greater than the cutoff wavelength of the absorption edge; the peak of the photoluminescence of the bifacial enhancement layer has a full width at half maximum of less than 100 nm; and wherein the bifacial enhancement layer comprises quantum dots, and wherein the quantum dots comprise cadmium and tellurium. ### Claim 2 (depends on 1) The photovoltaic device of claim 1, wherein short circuit current JscLoss due to absorption by the bifacial enhancement layer is less than 20 mA/cm2. ### Claim 3 (depends on 1) The photovoltaic device of claim 1, wherein the cutoff wavelength of the absorption edge is less than or equal to 800 nm. ### Claim 4 (depends on 1) The photovoltaic device of claim 1, comprising: a transparent conductive oxide positioned over a substrate and between the substrate and the absorber layer; and a back support positioned over the bifacial enhancement layer, wherein the back support has a transmittance of 85% or more to the wavelength of the peak of the photoluminescence of the bifacial enhancement layer. ### Claim 5 (depends on 1) The photovoltaic device of claim 1, comprising a conducting layer over the absorber layer, and between the absorber layer and the bifacial enhancement layer, wherein the conducting layer has a transmittance of 85% or more to the wavelength of the peak of the photoluminescence of the bifacial enhancement layer. ### Claim 6 (depends on 1) The photovoltaic device of claim 1, comprising a back contact layer adjacent to the absorber layer, and positioned between the bifacial enhancement layer and the absorber layer, wherein the back contact layer has a transmittance of 85% or more to the wavelength of the peak of the photoluminescence of the bifacial enhancement layer. ### Claim 7 (depends on 1) The photovoltaic device of claim 1, wherein the absorber layer comprises selenium. ### Claim 8 (depends on 7) The photovoltaic device of claim 7, wherein the absorber layer comprises cadmium and tellurium, and the average atomic percent of the selenium in the absorber layer is greater than 0 atomic percent and less than or equal to about 25 atomic percent. ### Claim 9 (depends on 1) The photovoltaic device of claim 1, wherein the quantum dots have an average diameter of less than 20 nm. ### Claim 10 (depends on 9) The photovoltaic device of claim 9, wherein the bifacial enhancement layer has a thickness between 50 to 200,000 times the average diameter of quantum dots. ### Claim 11 (depends on 9) The photovoltaic device of claim 9, comprising a conducting layer over the absorber layer, wherein the quantum dots directly contact the conducting layer. ### Claim 12 (depends on 9) The photovoltaic device of claim 9, comprising an interlayer positioned over the quantum dots. ### Claim 13 (depends on 12) The photovoltaic device of claim 12, wherein the interlayer directly contacts the quantum dots. ### Claim 14 (depends on 9) The photovoltaic device of claim 9, wherein the quantum dots have an average absorbance coefficient of at least 104 cm-1 to photons having wavelengths from 400 nm to 800 nm. ### Claim 15 (depends on 9) The photovoltaic device of claim 9, wherein the quantum dots fill at least 15% of the volume of the bifacial enhancement layer. ### Claim 16 (depends on 1) The photovoltaic device of claim 1, wherein at least 50% of the photons having wavelengths from 400 nm to 800 nm incident to the bifacial enhancement layer are converted into the peak of the photoluminescence. ### Claim 17 (depends on 1) The photovoltaic device of claim 1, wherein the wavelength of the peak of the photoluminescence between 825 nm and 875 nm. ### Claim 18 (depends on 1) The photovoltaic device of claim 1, wherein: the front interface has a front quantum efficiency profile; the back interface has a back quantum efficiency profile; and a full width at half maximum of the front quantum efficiency profile is at least 2 times larger than a full width at half maximum of the back quantum efficiency profile. ### Claim 19 (depends on 1) The photovoltaic device of claim 1, wherein: the front interface has a front quantum efficiency profile; the back interface has a back quantum efficiency profile; and a peak of the front quantum efficiency profile is greater than a peak of the back quantum efficiency profile. ### Claim 20 (depends on 1) The photovoltaic device of claim 1, wherein the peak of the photoluminescence of the bifacial enhancement layer has a full width at half maximum in a range from 10 nm to 50 nm.