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Title: Effect of Sb on the Properties of GaInP Top Cells

Abstract

It is well known that the efficiency of GaInP/GaAs tandem solar cells is limited by the band gap of the GaInP top cell, which, in turn, is determined by the degree of compositional ordering in the GaInP base layer. Attempts to raise the band gap by the addition of Al to the top cell have met with limited success due to the strong affinity between Al and oxygen. Here we investigate a different approach. It has been shown that the presence of antimony on the surface of GaInP during its growth suppresses the ordering process and increases the band gap. In this paper, we study the effects of Sb on the properties of GaInP top cells. We show that, in addition to raising the band gap of GaInP, it also increases the incorporation of Zn and changes the relative incorporation of Ga and In. These effects depend strongly on the substrate orientation, growth temperature and rate, and the Sb/P ratio in the gas phase. We show that the band gap of the GaInP top cell (and the Voc) can be increased without reducing the minority carrier collection efficiency. The implications of these results are presented and discussed.

Authors:
; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
943988
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: [Proceedings] 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4), 7-12 May 2006, Waikoloa, Hawaii; Related Information: For preprint version see NREL/CP-520-39903
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; AFFINITY; ANTIMONY; EFFICIENCY; ENERGY CONVERSION; ORGANIC COMPOUNDS; ORIENTATION; OXYGEN; SOLAR CELLS; SUBSTRATES; VOLATILE MATTER; Solar Energy - Photovoltaics

Citation Formats

Olson, J. M., McMahon, W. E., and Kurtz, S. Effect of Sb on the Properties of GaInP Top Cells. United States: N. p., 2006. Web. doi:10.1109/WCPEC.2006.279574.
Olson, J. M., McMahon, W. E., & Kurtz, S. Effect of Sb on the Properties of GaInP Top Cells. United States. doi:10.1109/WCPEC.2006.279574.
Olson, J. M., McMahon, W. E., and Kurtz, S. Sun . "Effect of Sb on the Properties of GaInP Top Cells". United States. doi:10.1109/WCPEC.2006.279574.
@article{osti_943988,
title = {Effect of Sb on the Properties of GaInP Top Cells},
author = {Olson, J. M. and McMahon, W. E. and Kurtz, S.},
abstractNote = {It is well known that the efficiency of GaInP/GaAs tandem solar cells is limited by the band gap of the GaInP top cell, which, in turn, is determined by the degree of compositional ordering in the GaInP base layer. Attempts to raise the band gap by the addition of Al to the top cell have met with limited success due to the strong affinity between Al and oxygen. Here we investigate a different approach. It has been shown that the presence of antimony on the surface of GaInP during its growth suppresses the ordering process and increases the band gap. In this paper, we study the effects of Sb on the properties of GaInP top cells. We show that, in addition to raising the band gap of GaInP, it also increases the incorporation of Zn and changes the relative incorporation of Ga and In. These effects depend strongly on the substrate orientation, growth temperature and rate, and the Sb/P ratio in the gas phase. We show that the band gap of the GaInP top cell (and the Voc) can be increased without reducing the minority carrier collection efficiency. The implications of these results are presented and discussed.},
doi = {10.1109/WCPEC.2006.279574},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Conference:
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  • It is well known that the efficiency of GaInP/GaAs tandem solar cells is limited by the band gap of the GaInP top cell, which, in turn, is determined by the degree of compositional ordering in GaInP base layer. Attempts to raise the band gap by the addition of Al to the top cell have met with limited success due to the strong affinity between Al and oxygen. Here we investigate a different approach. It has been shown that the presence of antimony on the surface of GaInP during its growth suppresses the ordering process and increases the band gap. Inmore » this paper, we study the effects of Sb on the properties of GaInP top cells. We show that, in addition to raising the band gap of GaInP, it also increases the incorporation of Zn and changes the relative incorporation of Ga and In. These effects depend strongly on the substrate orientation, growth temperature and rate, and the Sb/P ratio in the gas phase. We show that the band gap of the GaInP top cell (and the Voc) can be increased without reducing the minority carrier collection efficiency. The implications of these results are presented and discussed.« less
  • The summary of this report is that: (1) Sb can be used to increase V{sub oc} of a GaInP top cell; (2) the photovoltaic quality of GaInP is relatively unaffected by the presence of Sb; and (3) Sb-doped GaInP/GaAs tandem cells show promise for achieving efficiencies over 32%.
  • Pt-PZT-Metal capacitors were prepared utilizing various top metallizations and PZT films which were previously fired to 700C to convert them into single-phase perovskite films. The dielectric (e.g. dielectric constants and leakage characteristics) and FE (e.g. remanent polarization and coercive field) properties were highly dependent in the choice of metals used. The highest dielectric constants were obtained for capacitors having noble or transition metals; the lowest leakage currents were obtained using Au or Pt top electrodes; and the highest polarizations (both remanent and spontaneous) were measured for capacitors having noble metals or Bi. There was not a consistent dependence of thesemore » properties (especially leakage currents) on the work function of the metal used. The electronegativity or affinity for oxygen of the electrode plays a more important role in affecting the junction characteristics. For several reactive top metals such as In, Zn, Cu and Al, the formation of interfacial oxide layers at the Pt-metal junctions leads to high values of coercive field ({approx}50kV/cm) compared to when noble metals or Zn are used ({approx}20-25kV/cm). The overall best dielectric and FE behaviors are derived from capacitors having noble metals, especially Pt, as the top and bottom electrodes.« less
  • We discuss the initial development of a concentrator device based on the GaInP/GaAs monolithic tandem cell structure. The very high one-sun efficiency of this device, coupled with its characteristic low operating current, make this a promising candidate for use under high concentration. Test results for a prototype device are presented. This device achieves an efficiency of 29.5% at a concentration of 102 suns.
  • In recent years, Ga(0.5)In(0.5)P/GaAs cells have drawn increased attention both because of their high efficiencies and because they are well suited for space applications. They can be grown and processed as two-junction devices with roughly twice the voltage and half the current of GaAs cells. They have low temperature coefficients, and have good potential for radiation hardness. The authors have previously reported the effects of electron irradiation on test cells which were not optimally designed for space. From those results they estimated that an optimally designed cell could achieve 20 percent after irradiation with 10(exp 15) cm(exp -2) 1 MeVmore » electrons. Modeling studies predicted that slightly higher efficiencies may be achievable. Record efficiencies for EOL performance of other types of cells are significantly lower. Even the best Si and InP cells have BOL efficiencies lower than the EOL efficiency they report here. Good GaAs cells have an EOL efficiency of 16 percent. The InP/Ga(0.5)In(0.5)As two-junction, two-terminal device has a BOL efficiency as high as 22.2 percent, but radiation results for these cells were limited. In this study the authors use the previous modeling and irradiation results to design a set of Ga(0.5)In(0.5)P/GaAs cells that will demonstrate the importance of the design parameters and result in high-efficiency devices. They report record AMO efficiencies: a BOL efficiency of 25.7 percent for a device optimized for BOL performance and two of different designs with EOL efficiencies of 19.6 percent (at 10(exp 15) cm(exp -2) 1 MeV electrons). They vary the bottom-cell base doping and the top-cell thickness to show the effects of these two important design parameters. They get an unexpected result indicating that the dopant added to the bottom-cell base also increases the degradation of the top cell.« less