Polarimetric measurements of the bright triplet emission of single cesium lead halide perovskite quantum dots at cryogenic temperature

Abstract

Cesium lead halide perovskite quantum dots (QDs) have recently emerged as promising platform for quantum light sources. Indeed, they exhibit exceptional photoluminescence properties thanks to the emission from a bright triplet exciton state [1]. The energetic fine structure splitting, in the order of a few millielectronvolts, can be revealed by performing single QD spectroscopy at cryogenic temperature. In particular, depending on the QD orientation and on the observation direction, up to three orthogonal emitting dipoles can be spectrally detected, each of them with a high degree of linear polarization. To measure the polarization of the exciton fine structure, typically a rotating linear polarizer was used. However, this method cannot provide a complete characterization of the polarization state of the emitted light, and the polarization properties of the small, non-linearly polarized fraction of the emission were unclear. That is why in this work we are investigating the polarization properties of individual cesium lead halide perovskite QDs by more advanced polarimetric techniques that allow to measure the complete Stokes polarization vector at cryogenic temperature for each emission line. For these measurements it is crucial to perform a careful calibration of the optical path with respect to residual, unwanted birefringent phase shifts that are often occurring from optical coatings. Moreover, these measurements require colloidal QDs with very low intermittent emission fluctuations. In my presentation I will report the results of the polarimetry of single perovskite QDs, shedding light on the non-linearly polarized emission fraction and the nature of their peculiar emission properties.