First-principles materials design of CuInSe2-based high-efficiency photovoltaic solar cells

Based on ab initio electronic structure calculations by self-interaction-corrected local-density-approximation (SIC-LDA) with the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA), we propose a materials design for high efficiency photovoltaic solar cells (PVSCs). It is shown that (i) the concentration dependence of the mixing energy of CuIn1-xGaxSe2 shows upward convexity, thus this system favors phase separation. Due to the type II band alignment between CuInSe2 and CuGaSe2, efficient electron-hole separation is realized in decomposed phase of this system. (ii) CuIn1-xZn0.5xSn0.5xSe2 has a direct band gap and no impurity state appears in the gap. Therefore, cost reduction is possible by using Zn and Sn instead of In. (iii) n-type CuAl1-xSnxS2 and p-type Cu1-xVCuxAlS2 have negative activation energy for doped impurities and are expected to be low-resistive transparent conducting sulfides, which should be useful for CuInSe2-based PVSCs. (C) 2011 Elsevier B.V. All rights reserved.