Nonlocal interaction enhanced biexciton emission in large CsPbBr₃ nanocrystals

Biexciton emission in quantum dots is an efficient way to generate entangled photon pairs, which are key resources in quantum informatics. Compared with epitaxial grown quantum dots, chemically synthesized colloidal quantum dots show advantages of tunable wavelength and easy integration to realize quantum light sources. However, biexciton efficiency of colloidal quantum dots has been limited by Auger recombination. In this paper, we reported nonlocal interaction enhanced biexciton emission with efficiency up to 80% in large perovskite nanocrystals (> 20 nm). The nonlocal interaction between carriers and excitons leads to the abnormal exponential decrease of Auger recombination with volume in large nanocrystals, which distinguishes with the linear scaling in small counterparts. Such an exponential decrease of Auger recombination results in long lifetime of biexcitons, responsible for the required high biexciton efficiency. The discovery of nonlocal effects in large semiconductor nanocrystals provides new strategies to achieve high efficiency multiple excitons for quantum optics and energy conversation applications.