Ultrafast exciton transfer in perovskite CsPbBr quantum dots and topological insulator BiSe film heterostructure.

Recently, topological insulator based heterostructures (HSs) have attracted tremendous research interest, due to their efficient carrier transfer features at the heterointerface induced by metallic surface states. Here, a novel HS comprising 0D perovskite CsPbBr quantum dots (QDs) and 2D material topological insulator BiSe film is proposed and experimentally investigated. Specifically, steady state and time-resolved photoluminescence (PL) measurements are employed, from which a significant quenching behaviour is observed in the HS, with an average quenching factor of 93.2 ± 0.8%. Additionally, time-resolved PL spectroscopy affirms that the carrier transfer efficiency can be up to 92.6 ± 0.2%. Furthermore, the dynamics of carrier transfer within the 0D-2D HS are characterized by utilizing femtosecond broadband transient absorption (TA) spectroscopy, revealing an ultrafast exciton transfer from photoexcited CsPbBr QDs to the BiSe film with a time-scale around 1.1 ± 0.2 ps. An alternative important finding is that the band renormalization is exhibited in CsPbBr QDs of the HS, with the dominant factor being the Coulomb screening effect. This work is expected to provide some fundamental understanding of the ultrafast and efficient carrier transfer mechanism underneath HSs based on topological insulators.