Colloidal CuZnSn(S,Se)-Au nano-heterostructures for inorganic perovskite photovoltaic applications as photocathode alternative.

We concretely report feasible synthesis procedures of colloidal CuZnSn(S,Se)-Au (CZTSSe-Au) nano-heterostructured composites, and creatively employ them as the counter electrodes (CEs) of all-solid-state solar cells with inorganic CsSnIF perovskite hole conductor. Acquired optical characterization indicates that integration of noble metal nanoparticles with cuprum-chalcogenide could heighten light absorption within visible-band due to localized surface plasmon resonance (LSPR) generated by Au, and the forbidden gap of nanocomposites gets adjustment accordingly. It is demonstrated that this novel photocathode alternative with favorable conductivity can not only match the energy level within the device band structure construction, but also restrain recombination so that accelerate charge transfer and extraction occurring on the photocathode. The photocurrent and photoelectric conversion efficiency (PCE) of cells conjugating CZTS-Au photocathodes turn to be respectively 43% and 25% higher than those using pure CZTS. Moreover, it has been demonstrated that CZTS-Au, coupling very well with inorganic perovskite, owns comparable electrocatalytic performance and even higher output photocurrent with respect to platinum CEs, which portends a potential substitution for conventional costly photocathodes. A comprehensive analysis on impedance spectroscopy data is subsequently carried out for the sake of deep understanding charge accumulation and transfer response at CsSnIF/CE interface, attempting to orient further optimization of device performance.