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Title: Ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer

Abstract

This paper reports the proposal, design, and demonstration of ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer to optimize light management and minimize non-radiative recombination. According to our recently developed semi-analytical model, this design offers one of the highest potential achievable efficiencies for GaAs solar cells possessing typical non-radiative recombination rates found among commercially available III-V arsenide and phosphide materials. The structure of the demonstrated solar cells consists of an In{sub 0.49}Ga{sub 0.51}P/GaAs/In{sub 0.49}Ga{sub 0.51}P double-heterostructure PN junction with an ultra-thin 300 nm thick GaAs absorber, combined with a 5 μm thick Al{sub 0.52}In{sub 0.48}P layer with a textured as-grown surface coated with Au used as a reflective back scattering layer. The final devices were fabricated using a substrate-removal and flip-chip bonding process. Solar cells with a top metal contact coverage of 9.7%, and a MgF{sub 2}/ZnS anti-reflective coating demonstrated open-circuit voltages (V{sub oc}) up to 1.00 V, short-circuit current densities (J{sub sc}) up to 24.5 mA/cm{sup 2}, and power conversion efficiencies up to 19.1%; demonstrating the feasibility of this design approach. If a commonly used 2% metal grid coverage is assumed, the anticipated J{sub sc} and conversion efficiency of these devices are expected to reach 26.6 mA/cm{sup 2} and 20.7%,more » respectively.« less

Authors:
; ; ; ; ;  [1]; ;  [2]
  1. Center for Photonics Innovation and School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States)
  2. Sumika Electronic Materials, Inc., Phoenix, Arizona 85034 (United States)
Publication Date:
OSTI Identifier:
22304315
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BACKSCATTERING; CONNECTORS; CONVERSION; CURRENT DENSITY; ELECTRIC CONTACTS; ELECTRICAL FAULTS; GALLIUM ARSENIDES; GALLIUM PHOSPHIDES; HETEROJUNCTIONS; INDIUM COMPOUNDS; LAYERS; MAGNESIUM FLUORIDES; METALS; RECOMBINATION; SEMICONDUCTOR JUNCTIONS; SOLAR CELLS; SUBSTRATES; SUPERCONDUCTING JUNCTIONS; SURFACES; ZINC SULFIDES

Citation Formats

Yang, Weiquan, Becker, Jacob, Liu, Shi, Kuo, Ying-Shen, Li, Jing-Jing, Zhang, Yong-Hang, Landini, Barbara, and Campman, Ken. Ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer. United States: N. p., 2014. Web. doi:10.1063/1.4878156.
Yang, Weiquan, Becker, Jacob, Liu, Shi, Kuo, Ying-Shen, Li, Jing-Jing, Zhang, Yong-Hang, Landini, Barbara, & Campman, Ken. Ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer. United States. doi:10.1063/1.4878156.
Yang, Weiquan, Becker, Jacob, Liu, Shi, Kuo, Ying-Shen, Li, Jing-Jing, Zhang, Yong-Hang, Landini, Barbara, and Campman, Ken. 2014. "Ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer". United States. doi:10.1063/1.4878156.
@article{osti_22304315,
title = {Ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer},
author = {Yang, Weiquan and Becker, Jacob and Liu, Shi and Kuo, Ying-Shen and Li, Jing-Jing and Zhang, Yong-Hang and Landini, Barbara and Campman, Ken},
abstractNote = {This paper reports the proposal, design, and demonstration of ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer to optimize light management and minimize non-radiative recombination. According to our recently developed semi-analytical model, this design offers one of the highest potential achievable efficiencies for GaAs solar cells possessing typical non-radiative recombination rates found among commercially available III-V arsenide and phosphide materials. The structure of the demonstrated solar cells consists of an In{sub 0.49}Ga{sub 0.51}P/GaAs/In{sub 0.49}Ga{sub 0.51}P double-heterostructure PN junction with an ultra-thin 300 nm thick GaAs absorber, combined with a 5 μm thick Al{sub 0.52}In{sub 0.48}P layer with a textured as-grown surface coated with Au used as a reflective back scattering layer. The final devices were fabricated using a substrate-removal and flip-chip bonding process. Solar cells with a top metal contact coverage of 9.7%, and a MgF{sub 2}/ZnS anti-reflective coating demonstrated open-circuit voltages (V{sub oc}) up to 1.00 V, short-circuit current densities (J{sub sc}) up to 24.5 mA/cm{sup 2}, and power conversion efficiencies up to 19.1%; demonstrating the feasibility of this design approach. If a commonly used 2% metal grid coverage is assumed, the anticipated J{sub sc} and conversion efficiency of these devices are expected to reach 26.6 mA/cm{sup 2} and 20.7%, respectively.},
doi = {10.1063/1.4878156},
journal = {Journal of Applied Physics},
number = 20,
volume = 115,
place = {United States},
year = 2014,
month = 5
}
  • A study of the performance of single-junction InGaP/GaAs and dual-junction InGaP/GaAs tandem cells under low concentration ratios (up to 15 suns), before and after 1 MeV electron irradiation is presented. Analysis of the tunnel junction parameters under different concentrated light illuminations reveals that the peak current (J{sub P}) and valley current (J{sub V}) densities should be greater than the short-circuit current density (J{sub sc}) for better performance. The tunnel junction behavior against light intensity improved after irradiation. This led to the suggestion that the peak current density (J{sub P}) and valley current density (J{sub V}) of the tunnel junction weremore » enhanced after irradiation or the peak current was shifted to higher concentration. The recovery of the radiation damage under concentrated light illumination conditions suggests that the performance of the InGaP/GaAs tandem solar cell can be enhanced even under low concentration ratios.« less
  • Thin-layer silicon solar cells utilize surface textures to increase light absorption and back surface fields to prevent recombination at the silicon-substrate interface. The authors present an analytical model for the internal quantum efficiency that accounts for light trapping and also considers carrier generation and recombination in back surface fields or substrates. They introduce a graphical representation of experimental data, the so-called Parameter-Confidence-Plot, which allows one to draw maximum information on diffusion lengths and surface recombination velocities from quantum efficiency measurements. The analysis is exemplified for state of the art thin-layer silicon solar cells with and without back surface fields.
  • The full potential of thin-film, CdS/CdTe photovoltaic solar cells will not be realized until issues relating to the fabrication of environmentally stable, low-resistance, and easily manufactured contacts to the {ital p}-CdTe layer are addressed. One alternative that provides the required contact parameters employs a Cu-doped ZnTe(ZnTe:Cu) interface layer between the {ital p}-CdTe and the outer metal contact. Thin films of ZnTe:Cu containing various concentrations of metallic Cu are produced by rf-magnetron sputtering. Additionally, the effect of incorporating small amounts of excess Zn into the sputtering target is studied. We find that the electrical resistivity of ZnTe:Cu films deposited at 300{degree}C,more » and prepared with Cu concentrations of {approximately}0.45 at.{percent}, is much higher than would be expected from studies of films doped with higher Cu concentrations ({approximately}6 at.{percent} Cu). We also find that postdeposition heat treatment significantly reduces the electrical resistivity of the films containing {approximately}0.45 at.{percent} Cu. However, compositional analysis indicates that the surface of the films become increasingly enriched in Zn at annealing temperatures {approx_gt}350{degree}C. Analysis of the hole effective mass ({ital m}{sub {ital h}}) for films containing {approximately}6 at.{percent} Cu indicates a value for {ital m}{sub {ital h}} of 0.35 {ital m}{sub {ital e}}, and a high-frequency dielectric constant ({var_epsilon}{sub {infinity}}) of 8.2.« less