Nonlinear optical absorption and ultrafast carrier dynamics of copper antimony sulfide semiconductor nanocrystals

Ternary copper antimony sulfide nanocrystals (CAS NCs), a promising solar cell candidate, have been proposed and investigated from the perspective of synthesis method, linear optical response, and size and band structure tunability. Herein, we present the intensity related nonlinear absorption using the Z-scan technique. Electron and hole relaxation dynamics for the as-prepared three phases, CuSbS2, Cu3SbS4 and Cu(12)Sb4S(13) NCs, are studied at the visible spectrum band. With the assistance of fs-resolved transient absorption spectrum technology, photon induced charge carrier dynamics within the valence/conduction band and trap states are analyzed and attributed to three relaxation processes, the corresponding lifetimes of which are approximate to 400 fs, approximate to 5 ps and approximate to 60 ps, respectively. This analysis on electron and hole spatial separation and recombination is significant for the improvement of CAS NC based devices, and paves the way for the application of semiconductor NCs in photovoltaic devices, optical detection and other optoelectronic devices.