Spin-enabled photochemistry using nanocrystal-molecule hybrids

Research interest in the spin properties of lead halide perovskites has been rising in recent years in the hope of using solution-processed materials for scalable implementation of spintronics and quantum information technologies. However, very short spin lifetimes are often found for these systems, suggesting a long way to go along this direction. Here, we propose that these short spin lifetimes can instead find immediate applications in molecular photochemistry that largely relies on spin-relaxed triplet excited states. We demonstrated this using CsPbBr3 nanocrystals interfaced with rhodamine B (RhB) molecules. Photoexcitation of RhB led to hole injection into nanocrystals; rapid hole spin-flip and subsequent recombination of the charge-separated states efficiently populated RhB triplets. Photoexcitation of CsPbBr3 nanocrystals also produced RhB triplets through a similar mechanism. Because of the complementary spectral coverage of CsPbBr3 and RhB, we achieved efficient white-light-driven triplet-fusion photon upconversion and singlet-oxygen generation using triplets from the nanocrystal-molecule hybrids.