Biexciton-Like Auger Blinking in Strongly Confined CsPbBr3 Perovskite Quantum Dots

Single perovskite quantum dots (QDs) are notorious for their poor stability. As a result, surface defects will be generated and this will lead to trion formation that reduces fluorescence intensity, setting barriers to exploring the intrinsic exciton dynamics and the applications of perovskite QDs in single-photon sources. Here we demonstrate that strongly confined CsPbBr3 perovskite QDs (SCPQDs) embedded in a matrix formed by phenethylammonium bromide exhibit suppressed trion formation and remain photostable under intense photoexcitation. The increased surface passivation and stability enables the study of multi-exciton interactions in SCPQDs. We found that, in well-passivated SCPQDs, increasing excitation rates leads to weak fluorescence intensity fluctuations accompanied by an unusual spectral blueshift in the photoluminescence. We attribute this to a biexciton-like Auger interaction between excitons and trapped excitons formed by surface lattice elastic distortions. This hypothesis is corroborated by the unique repulsive biexciton interaction in SCPQDs. Our study provides insights into the fundamental multi-exciton interactions in SCPQDs and will advance the development of quantum light sources based on perovskite QDs.