Structural and optical properties of CdS/Cu[Se.sub.2] heterostructures irradiated by high-energy electrons

Thin films of Cu(In, Ga)[Se.sub.2] (CIGS) with a Ga/(Ga + In) ratio of ~0.27 corresponding to the standard elemental composition for solar-energy transducers were grown on Mo-coated glass substrates by the Cu, In, Ga, and Se co-evaporation technique from different sources. Transmission (T), photoluminescence (PL), and photoluminescence excitation (PLE) spectra at 4.2 K were used to analyze electronic properties in the as-grown and electron-irradiated CIGS films. The band-gap energy ([E.sub.g]) of the CIGS films measured using both transmission and PLE methods was found to be about 1.28 eV at 4.2 K. Two deep bands in the PL spectra of the irradiated CIGS films, [P.sub.1] at ~0.91 eV and [P.sub.2] at ~0.77 eV, have been detected. These bands are tentatively associated with copper atoms substituting indium ([Cu.sub.In]) and indium vacancies [V.sub.In], respectively, as the simplest radiation-induced defects.