Interface passivation and band alignment of high efficiency Cu(In, Ga)Se2 solar cells: Application of Mo(OxSe1-x)2 buffer layer at Mo/ Cu(In, Ga)Se2 interface

Abstract

Cu(In,Ga)Se2(CIGSe) solar cell is one of the most promising thin film solar cells with high photoelectric conversion efficiency. However, the efficiency is still far below the thermodynamic Shockley−Queisser (SQ) limit. Interfacial recombination is the main factor restricting the performance of CIGSe solar cells. In this work, oxygen-doped Mo(OxSe1-x)2 was employed to study the effect of Mo/CIGSe interfacial recombination. SCAPS simulation and first-principles calculation were used in this work. The band gap of Mo(OxSe1-x)2 was adjusted by changing the content of oxygen, the band alignment of Mo/Mo(OxSe1-x)2 interface and Mo(OxSe1-x)2/CIGSe interface were optimized. The back interface recombination was effectively reduced by using a thickness of 10–70 nm Mo(OxSe1-x)2 with an oxygen doping concentration of 12.5%–50.0% and the performance of CIGSe solar cells was improved. Finally, the conversion efficiency was improved from 15.80% to 24.35% with oxygen doping concentration of 25% and Mo(OxSe1-x)2 layer with thickness of 40 nm.