Deposition of CuIn(Se, S)_2 thin films by sulfurization of selenized Cu/In alloys

摘要

The relatively small band gap values (close to 1eV) of CuInSe_2 thin films limits the conversion efficiencies of completed CuInSe_2/CdS/ZnO solar cell devices. In the case of traditional two-stage growth techniques, limited success has been achieved to increase the band gap by substituting indium with gallium. In this study, sputtered copper-indium alloys were exposed to a H_2Se/Ar atmosphere under defined conditions in order to produce partially reacted CuInSe_2 structures. These films were subsequently exposed to a H_2S/Ar atmosphere to produce monophasic CuIn(Se, S)_2 quaternary alloys. The homogeneous incorporation of S into CuInSe_2 led to a systematic shift in the lattice parameters and band gap of the absorber films. From these studies optimum selenization/sulfurization conditions were determined for the deposition of homogeneous CuIn(Se, S)_2 thin films with an optimum band gap values between 1.15 and 1.2 eV.