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Title: Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006

Abstract

Goal is to demo realistic path to III-V multijunction concentrator efficiencies > 40% by substrate-engineering combining compositional grading with patterned epitaxy for small-area cells for high concentration.

Authors:
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
942086
Report Number(s):
NREL/SR-520-44250
XAT-4-33624-14; TRN: US200902%%89
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Technical Report
Resource Relation:
Related Information: Work performed by The Ohio State University, Columbus, Ohio
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; BUFFERS; CONCENTRATION RATIO; CONCENTRATOR SOLAR CELLS; CONCENTRATORS; DISLOCATIONS; EFFICIENCY; EPITAXY; RESEARCH PROGRAMS; SOLAR CELLS; SUBSTRATES; THERMAL CONDUCTIVITY; PV; III-V MULTIJUNCTION CONCENTRATOR; GE SUBTRATE; LATTICE MATCH; DUAL JUNCTION; PATTERNED SI:GE/SI; COMPOSITIONAL GRADING; INGAP/INGAAS; SMALL AREA; Solar Energy - Photovoltaics

Citation Formats

Ringel, S. A. Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006. United States: N. p., 2008. Web. doi:10.2172/942086.
Ringel, S. A. Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006. United States. doi:10.2172/942086.
Ringel, S. A. 2008. "Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006". United States. doi:10.2172/942086. https://www.osti.gov/servlets/purl/942086.
@article{osti_942086,
title = {Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006},
author = {Ringel, S. A.},
abstractNote = {Goal is to demo realistic path to III-V multijunction concentrator efficiencies > 40% by substrate-engineering combining compositional grading with patterned epitaxy for small-area cells for high concentration.},
doi = {10.2172/942086},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2008,
month =
}

Technical Report:

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  • In high growth rate ({ge} 50 {angstrom}/s) HW-CVD a-Si:H films, for the first time, we show gaseous molecules in nanovoids ({approx}2% volume fraction of tube-like nanoscale voids), and demonstrate that confinement on the nanometer scale generates NMR effects that have never been observed in macroscopic systems. In the same system we found the PL peak red shift. We suggest that highly strained bonds on the inner surfaces of the nanoscale voids form broad conduction-band tail states that are responsible for the PL red shift. We characterized the structural transition from a- to nc-Si as function of H-dilution, thickness and T{submore » s} of both HW- and PE-CVD films using IR, Raman, PL, CPM/PDS and E{sub a} et al. We found not only the c-Si volume fraction but also the g.b. and microstructures play an important role in the properties of the i-layer and their solar cell performance. We found a narrow structural transition zone in which the bond-angle variation, {Delta}{Theta}, decreases from 10{sup o} to 8{sup o}. For nc-Si samples, we found a characteristic low energy PL peak and proved that is originated from the g.b. regions. Using micro-Raman, we found the structural non-uniformity in the mixed-phase solar cells that showed V{sub oc} enhancement after light soaking. Using micro-Raman, we also found the slight increase of crystallinity in M/{mu}c-Si/M devices after current forming.« less
  • UC-Berkeley study of transition metal related defects in PV-grade mc-Si to understand their pathways into solar cells; chemical state/distribution; interaction with structural defects; defect engineering.
  • Results for a-Si characteristics/modeling; photocarrier drift mobilities in a-Si;H, ..mu..c-Si:H, CIGS; hole-conducting polymers as p-layer for a-Si and c-Si; IR spectra of p/i and n/i interfaces in a-Si.
  • The benefits of mechanically stacked tandem concentrator solar cells were first demonstrated on a NASA mission in 1994. In that case, transparent GaAs cells were stacked on top of infrared-sensitive GaSb booster cells and arrayed in a point-focus solar concentrator module. The results were high efficiency, excellent radiation resistance and high voltage tolerance, all of which sustained some interest in concentrator arrays. Since then, the lens design has evolved to a linear geometry used with high efficiency nontransparent GaInP{sub 2}/GaAs cells on germanium substrates. These high bandgap dual junction cells still leave about 35% of the sun`s longer wavelength energymore » uncollected. The proposal for this contract was to make the dual junction cell transparent to that long wavelength range and stack it on a GaSb booster cell for added efficiency gains. Tecstar made the transparent dual junction GaInP{sub 2}/GaAs cells on GaAs substrates as a subcontractor, and JX Crystals took on the tasks of booster cell fabrication as well as assembly and testing for this Phase 1 effort. Resulting dual junction cells achieved efficiencies of 29.6% at a 15 sun concentration level.« less
  • Development of a mechanically-stacked, multijunction solar cell is described. The cell uses a thin, high-bandgap cell bonded to the top of a silicon cell. Two electrical leads are brought out from each cell in the stack so that the cells may be operated electrically in parallel while they are optically in series. This report discusses modeling and packaging of the cascaded cells. It also describes a process for making a thin, high-bandgap AlGaAs solar cell.