Cu(In,Ga)S2 Phase Formation from Metallic Cu-In-Ga Precursor Stacks in Rapid Thermal Processes

Abstract

ABSTRACTThis contribution compares the growth of Cu(Ga,In)S2 based thin film solar cell absorbers in rapid thermal systems using sulfur vapor Sx or H2S/Ar as reactive atmosphere, focusing on Ga-related influences on film growth and phase formation. Cu-In alloying in the precursor is kinetically hindered by the presence of Cu-Ga phases. In sulfur vapor Ga-containing samples sulfurize via an intermediate CuIn2S8 phase, thereby delaying the full sulfurization and recrystallization of the layer. In contrast, in H2S/Ar fast Ga-In interdiffusion and no intermediate chalcogenide phases are observed. The inhomogeneous Ga depth distribution usually reported for sequentially prepared Cu(In,Ga)S2 films can be assigned to the segregation of CuGaS2 prior to CuInS2.