Electron-acceptor organic molecules have been shown recently to quench the photoluminescence (PL) of CsPbBr 3 perovskite nanocrystals (NC). The phenomenon has been attributed to electron-transfer from the CsPbBr 3 NC to the surface-bound acceptor. Here we exploit the use of naphthalenediimides (NDI) as electron-acceptors for CsPbBr 3 NC. For this purpose, we employed N,N′-bis(3-triethoxysilylpropyl)-1,4,5,8-naphthalenediimide (SNDI), a NDI derivative bearing hydrolysable silane groups, which was synthesized by our group. Addition of SNDI to a toluene solution of CsPbBr 3 NC resulted in blue-shifts in both absorbance and PL maxima, concomitant with PL quenching, suggesting binding of SNDI to the surface of the NC. The observed blue-shifts indicate electronic coupling between the SNDI ligand and the NC. Time resolved PL experiments did not show a faster decay upon addition of SNDI to the CsPbBr 3 NC, indicating the static nature of the quenching. Complex formation between SNDI and CsPbBr 3 NC was further studied by infrared spectroscopy, which showed that the silane groups underwent hydrolysis upon binding to the NC. Electrochemical measurements, along with the optical data, allowed the construction of an energy level diagram, which shows that the conduction band of the perovskite lies higher in energy than the LUMO of SNDI, making electron transfer a thermodynamically favorable process. These results place SNDI as a suitable candidate for ETL in perovskite based solar cells. • Complex formation between a silylated naphthalenediimide and CsPbBr 3 was observed • The fluorescence of perovskite nanocrystals was quenched by a naphthalenediimide • Photoinduced electron transfer from the naphthalenediimide to CsPbBr 3 was observed
Souza et al. (Sun,) studied this question.