The effects of Cu composition on the structural, morphological, optical properties of Cu2ZnSnS4 (CZTS)
films prepared by RF magnetron sputtering and a post sulfurization, and CZTS solar cells performance
have been investigated. The crystal structure characterized by XRD patterns, Raman and far-infrared
spectra reveal that the secondary phases (e.g. SnS and Cu2SnS3) can be suppressed effectively by
manipulating the Cu content in CZTS thin films. Furthermore, morphological studies indicate that the
CZTS thin film with low Cu content shows a bilayer structure, while that with high Cu content exhibits
the grain growth throughout the entire absorber film with some voids at the Mo/CZTS interface. Finally, a
Cu-poor CZTS solar cell with 3.46% is fabricated. Temperature and excitation-power dependent Photoluminescence
measurement reveals the radiative recombination between electrons in conduction band
tails and holes bound to the neighboring acceptors levels in Cu-poor CZTS device. The diode parameters
of Cu-poor CZTS solar cell are extracted and used to discuss the possible reason for limiting efficiency.