CsPbBr₃–Ti₃C₂T<i>_x</i> MXene QD/QD Heterojunction: Photoluminescence Quenching, Charge Transfer, and Cd Ion Sensing Application

A van der Waals heterostructure between all-inorganic CsPbBr3 halide perovskite quantum dots (CPB QDs) and Ti3C2Tx MXene (MXN) QDs is realized, and the photophysics of the composite is examined. A strong quenching of the steady-state photoluminescence of the perovskite QDs is observed, which is further examined by a time-resolved photoluminescence study. It is attributed to the charge transfer from CPB to MXN QDs followed by rapid energy relaxation of hot electrons and hot holes toward the band edge, leading to their recombination with photon energy in the far-IR energy domain. It is further shown that the CPB–MXN QD/QD system acts as an excellent on–off–on photoluminescence probe for cadmium ion detection and also as an active material for photodetector application.