Trion Mediated Sequential Charge Separation in Functionalized CsPbBr₃/AgInS₂ Hybrid Nanocrystals

Charge transfer in colloidal hybrid nanostructures is often governed not only by band alignment but also by the nature of the interfacial excited state. Here, we examine how 4-aminothiophenol (ATP) functionalization of CsPbBr₃ nanocrystals (CPB NCs) modulates the electron-transfer process to AgInS₂ quantum dots (AIS QDs). In the unfunctionalized CPB-AIS assembly, photoluminescence quenching and time-resolved measurements indicate only weak electron transfer from CPB to AIS despite thermodynamically favorable band alignment. Upon functionalization, ATP extracts a photogenerated hole from CPB on the ∼2 ps time scale, generating a charge-separated CPB-ATP state with a residual electron on CPB. Femtosecond transient absorption measurement shows that this process is accompanied by the appearance of a trion state, which then mediates the electron transfer to the AIS in the functionalized CPB. As a result, the CPB-ATP-AIS hybrid exhibits nearly complete photoluminescence quenching, a pronounced shortening of photoluminescence lifetime, and enhanced photocurrent relative to CPB-AIS. These results show that ATP functionalization alters the carrier relaxation pathway of CPB and thereby enables more efficient sequential charge separation.