Multiband Formation in Cr doped CuGaS2 Thin Films Synthesized by Chemical Spray Pyrolysis

We study the formation of multiband electronic structures for Cr doped chalcopyrite CuGaS
₂
thin films synthesized by chemical spray pyrolysis. Electronic transition studies using photo-modulated reflectance (PR) spectra revealed that the bandgaps were widened when Cr was added, and were accompanied by a new transition due to intermediate bands (IB) formation within the bandgap. This is in consistent with our calculation based on density functional theory. PR transitions due to native defects were prominent for pure CuGaS
₂
thin films, and their transition strengths were reduced in the Cr added films. These observations are consistent with photo-luminescence (PL) spectra measured at room temperature.