Excitonic effects in the linear and nonlinear optical properties of ZnO@WS2 heterojunction films under photoexcitation

The excitation effects of linear and nonlinear optical properties for the [email protected]2 heterojunction (ZWH) films under photoexcitation were studied. We found that intrinsic absorption and radiation of ZWH films from bandgap and defects of ZnO and WS2. "M" and "W" type of Z-scan curve represent mechanism of TPA/3PA induced the ground state/excited state SA or RSA. The transient absorption spectra corresponding to free carriers, trapped carriers, and state filling were observed in the picosecond time region for samples. Our results revealed the carrier relaxation and recombination processes in WS2 and ZWH films, identifying the critical role of stoichiometry in photo-induced phenomena.