Photoluminescence properties of CuInSe2 grown by molecular beam epitaxy

Photoluminescence (PL) properties of CuInSe 2 thin films with Cu/In ratio ranging from 0.81 to 1.81 grown by molecular beam epitaxy have been investigated for photovoltaic applications. The PL spectra of Cu-rich CuInSe 2 epitaxial films unlike those of polycrystalline CuInSe 2 showed well-defined emission lines, suggesting that high quality CuInSe 2 epitaxial films have been grown. Such fine PL spectra made the identification possible of phono replicas, in other words, the separation of such phonon replicas from substantive emmissions. PL properties are found to be very sensitive to the growth parameters such as Cu/In ratio and substrate temperature. A broad peak at λ ∼ 1.45 μm becomes dominant in In-rich films, and excitation power dependence of such a broad emission indicated a pair-type radiative recombination, most likely the emission due to donor-acceptor pair or their complex.