Universal Inverse Scaling of Exciton-Exciton Annihilation Coefficient with Exciton Lifetime.

Be it for essential everyday applications such as bright light-emitting devices or to achieve Bose-Einstein condensation, materials in which high densities of excitons recombine radiatively are crucially important. However, in all excitonic materials, exciton-exciton annihilation (EEA) becomes the dominant loss mechanism at high densities. Typically, a macroscopic parameter named EEA coefficient (CEEA) is used to compare EEA rates between materials at the same density; higher CEEA implies higher EEA rate. Here, we find that the reported values of CEEA for 140 different materials is inversely related to the single-exciton lifetime. Since during EEA one exciton must relax to ground state, CEEA is proportional to the single-exciton recombination rate. This leads to the counterintuitive observation that the exciton density at which EEA starts to dominate is higher in a material with larger CEEA. These results broaden our understanding of EEA across different material systems and provide a vantage point for future excitonic materials and devices.