InGaAs/GaAsSb-interface studies in a tunnel junction of a low band gap tandem solar cell

被引:10
作者
Seidel, U. [1 ]
Sagol, B. E. [1 ]
Szabo, N. [1 ]
Schwarzburg, K. [1 ]
Hannappel, T. [1 ]
机构
[1] Hahn Meitner Inst Berlin GmbH, D-14109 Berlin, Germany
关键词
III-V solar cells; InP-based materials; metal organic chemical vapor deposition; metal organic vapor phase epitaxy; reflectance anisotropy spectroscopy; low energy electron diffiaction; surface reconstruction;
D O I
10.1016/j.tsf.2007.12.013
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
A low band gap InP-based double junction (2 J) solar cell was designed, realized and measured. The cell is supposed to work in a 4 junction configuration below an InGaP/GaAs 2 J solar cell. For the lower and higher band gap absorbers InGaAs (Eg=0.73 eV) and InGaAsP (Eg= 1.03 eV) were utilized, respectively. These two subcells were connected via a tunnel junction including thin, highly doped n-type InGaAs and p-type GaAsSb layers. The growth of GaAsSb layers on different InGaAs surface reconstructions (4 x 3), (2 x 4) and (4 x 2) was investigated with in-situ reflectance anisotropy spectroscopy (RAS). The optical signals were benchmarked in ultrahigh vacuum (UHV) with X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). The influence of different preparation procedures on the InGaAs/GaAsSb heterointerface and on the cell performance was investigated. XPS measurements revealed that the sharpest InGaAs/GaAsSb interface was achieved when the GaAsSb layer in the tunnel junction of the solar cell was grown on III-rich, i.e., (2 x 4)- or (4 x 2)-reconstructed InGaAs (100) surfaces. This was also confirmed by solar power conversion efficiency measurements of the solar cells, where slightly lower efficiencies were observed for the cells with the V-rich-prepared tunnel junction interfaces (4 x 3). (c) 2008 Published by Elsevier B.
引用
收藏
页码:6723 / 6728
页数:6
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