The achievement of size uniformity and monodispersity in perovskite quantum dots (QDs) requires the implementation of precise temperature control and the establishment of optimal reaction conditions. Nevertheless, the accurate control of a range of reaction variables represents a considerable challenge. This study addresses the aforementioned challenge by employing manganese (Mn) doping to achieve size uniformity in CsPbBr₃ perovskite QDs without the necessity for the precise control of the reaction conditions. By optimizing the Mn:Pb ratio, it is possible to successfully dope CsPbBr₃ QDs with the appropriate concentrations of Mn²⁺ and achieve a uniform size distribution. The spectroscopic measurements on single QDs indicate that the appropriate Mn²⁺ concentrations can result in a narrower spectral linewidth, a longer photoluminescence (PL) lifetime, and a reduced biexciton Auger recombination rate, thus positively affecting the PL properties. This study not only simplifies the size control of perovskite QDs but also demonstrates the potential of Mn-doped CsPbBr₃ QDs for narrow-linewidth light-emitting diode applications.

Determining the correlation between the size of a single quantum dot (QD) and its photoluminescence (PL) properties is a challenging task. In the study, we determine the size of each QD by measuring its absorption cross section, which allows for accurate investigation of size-dependent PL blinking mechanisms and volume scaling of the biexciton Auger recombination at the single-particle level. A significant correlation between the blinking mechanism and QD size is observed under low excitation conditions. When the QD size is smaller than their Bohr diameter, single CsPbI3 perovskite QDs tend to exhibit BC-blinking, whereas they tend to exhibit Auger-blinking when the QD size exceeds their Bohr diameter. In addition, by extracting bright-state photons from the PL intensity trajectories, the effects of QD charging and surface defects on the biexcitons are effectively reduced. This allows for a more accurate measurement of the volume scaling of biexciton Auger recombination in weakly confined CsPbI3 perovskite QDs at the single-dot level, revealing a superlinear volume scaling (τXX,Auger ∝ σ1.96).

Biexcitons play an important role in colloidal quantum dot (QD) applications. However, quantitative measurements of absolute biexciton quantum yields (QYs) have long been limited to extremely weak excitation conditions, which has hindered the study of biexciton dynamics and related applications. Here, we present a significant improvement to the time-resolved photon statistics method for measuring absolute biexciton QY. This improvement takes into account the contribution of biexciton emission to the rate of single-photon events, which enables the method to break the limitation of weak excitation conditions and measure the absolute biexciton QYs of single QDs under high excitation conditions. Using the measured QYs of both charged and neutral biexcitons at high excitation conditions, we can calculate the ratios of the radiative and Auger recombination rates of the two types of biexciton. These ratios are in agreement with the theoretical predictions of the asymmetric band structures of CdSe-based QDs, thereby verifying the accuracy and reliability of the method. Accurate measurement of absolute biexciton QYs under high excitation conditions enables the study of QD biexciton dynamics and applications based on biexcitons.