Tailoring Charge Donor-Acceptor Interaction in CsPbBr₃ Perovskite Nanocrystals through Ligand Exchange

The surface ligands in colloidal metal halide perovskites influence not only their intrinsic optoelectronic properties but also their interaction with other materials and molecules. Donor-acceptor interactions of CsPbBr₃ perovskite nanocrystals with TiO₂ nanoparticles and nanotubes are explored by replacing long-chain oleylamine ligands with short-chain butylamines. Through postsynthesis ligand exchange, the nanocrystals are functionalized with butylamine ligands while their intrinsic properties are maintained. In solution, butylamine-capped nanocrystals exhibit reduced photoluminescence intensity with increasing TiO₂ concentration but without any change in photoluminescence lifetime. Intriguingly, the Stern-Volmer plot depicts different slopes at low and high TiO₂ concentrations, suggesting donor-acceptor interaction through mixed static photoluminescence quenching and quenching sphere of action mechanism . Oleylamine-capped nanocrystals in solution, on the other hand, show no interaction with TiO₂, as indicated by consistent photoluminescence intensities and lifetimes before and after TiO₂ addition. In films, both types exhibit decreased photoluminescence lifetime with TiO₂, indicating enhanced donor-acceptor interaction, which is discussed in terms of electron transfer. TiO₂ nanotubes enhance nonradiative recombination more in butylamine-capped CsPbBr₃ perovskite nanocrystals, emphasizing the role of ligand chain length.