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International Journal of Photoenergy
Volume 2014 (2014), Article ID 186579, 6 pages
http://dx.doi.org/10.1155/2014/186579
Research Article

Device Modeling of the Performance of Cu(In,Ga)Se2 Solar Cells with V-Shaped Bandgap Profiles

1Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Taoyuan 333, Taiwan
2Department of Photonics and Institute of Electro-Optical Engineering, National Chiao-Tung University, 1001 Ta Hsueh Road, Hsinchu 30013, Taiwan
3Department of Photonics Engineering, Yuan-Ze University, 135 Yuan-Tung Road, Chung-Li 32003, Taiwan
4Advanced Optoelectronic Technology Center, National Cheng Kung University, No. 1 University Road, Tainan 701, Taiwan

Received 10 December 2013; Revised 3 May 2014; Accepted 6 May 2014; Published 14 July 2014

Academic Editor: Prakash Basnyat

Copyright © 2014 Shou-Yi Kuo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The effect of Cu(In,Ga)Se2 (CIGS) with V-shaped bandgap on device performance is investigated in detail. A series of Ga/(In+Ga) ratio are set to study the influence of V-shaped bandgap profile on the electricity of CIGS thin film solar cells. The modeling of device current density-voltage (J-V) curve and bandgap grading profile corresponded well to measurement results. Detailed characteristic and modeling results show that an increased gradient of bandgap from valley to the buffer layer CdS will result in a barrier and lead to an enhanced recombination in the valley. This phenomenon can be modified by the back electric field resulting from a gradient bandgap from valley (bandgap minimum) to the Mo back contact. These results indicate CIGS-based solar cells can achieve higher performance by optimizing the V-shaped bandgap profile.