|Minority carrier lifetime stability in polycrystalline Cu2ZnSnSe4 thin films|
|Marie Buffiere1,2, Guy Brammertz1, Abdel-Aziz El Mel3, Nick Lenaers1,2, Yi Ren1.2, Armin E. Zaghi1.2, Yves Mols1, Christine Koeble4, Jef Vleugels2, Marc Meuris1, Jef Poortmans1,2
1imec, partner of Solliance, Leuven, Belgium
/2Department of Metallurgy and Materials Engineering, K.U. Leuven, Leuven, Belgium
/3Chimie des Interactions Plasma-Surface (ChIPS), CIRMAP, University of Mons, Mons, Belgium
/4Helmholtz-Zentrum Berlin, Berlin, Germany
In order to offer a cheap and reliable alternative to Cu(In,Ga)(S,Se)2 (CIGS) or CdTe technologies for thin film solar cell processing, Cu2ZnSnSe4 (CZTSe) and Cu2ZnSnS4 (CZTS) are being extensively studied as possible absorber materials for photovoltaic devices. In this contribution, we address the issue of the stability over time of the electrical properties of as-deposited CZTSe absorbers grown using a two step process. Time-resolved photoluminescence analysis shows that as-grown CZTSe thin films degrade when they are exposed to air. The analysis of the films prior to degradation reveals relatively long lifetimes. The degradation significantly affects the performance of the related solar cells. Among all the chemical treatments tested to recover the lifetime of the samples after air exposure, the KCN etching seems to be the most efficient.