Doping MAPbBr$_3$ hybrid perovskites with CdSe/CdZnS quantum dots: from emissive thin-films to hybrid single-photon sources

Abstract

We report the first doping of crystalline methylammonium lead bromide (MAPbBr 3 ) perovskite thin-films with CdSe/CdZnS core/shell quantum dots (QDs), using a softchemistry method that preserves their high quantum yield and other remarkable fluorescence properties. Our approach produces MAPbBr 3 films of 100 nm thickness doped at volume ratios between 0.025 and 5 % with colloidal CdSe/CdZnS QDs whose organic ligands are exchanged with halide ions to allow for close contact between the QDs and the perovskite matrix. Ensemble photoluminescence (PL) measurements demonstrate the retained emission of the QDs after incorporation into the MAPbBr 3 matrix. Ensemble photoluminescence excitation (PLE) spectra exhibit signatures of wavelengthdependent coupling between the CdSe/CdZnS QDs and the MAPbBr 3 matrix, i. e., a transfer of excitation energy from matrix to QD or from QD to matrix. Spatiallyresolved PL experiments reveal a strong correlation between the positions of QDs and an enhancement of the PL signal of the matrix. Fluorescence lifetime imaging (FLIM) of the doped films furthermore show that the emission lifetime of MAPbBr 3 is slower in the vicinity of QDs, which, in combination with the increased PL signal of the matrix, suggests that QDs can act as local nucleation seeds that improve the crystallinity of MAPbBr 3 , thus boosting its emission quantum yield. Confocal PL-antibunching measurements provide clear evidence of single-photon emission from individual QDs in perovskite. Finally, the analysis of blinking statistics indicates an improvement of the photostability of individual QDs in perovskite as compared to bare CdSe/CdZnS QDs. At high CdSe/CdZnS QD doping levels, this work opens thus the route to hybrid solar concentrators for visible-light harvesting and hybrid-based LEDs. Finally, low-doping content would lead to hybrid single-photon sources embedded in field-effect devices for single charge control to serve as an alternative to solid-state quantum dots and open the route to build nanophotonic devices with high-quantum-yield CdSe-based colloidal QDs.