Measurement of absolute biexciton quantum yields in single quantum dots: Breaking the limitation of weak excitation conditions

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.