Cooperative Exciton Interactions in Perovskite Supercrystal Enable Superior Optical Gains

Colloidal perovskite nanocrystals (NCs) have revolutionized optoelectronic technologies, yet their lasing applications remain constrained by intrinsic biexciton Auger recombination. In this work, we leverage the cooperative exciton ensemble in CsPbBr₃ supercrystals (SCs) to bypass the limitations of single-nanocrystal physics. Transient absorption measurements reveal that SCs exhibit near-zero biexciton binding energy and reduced biexciton Auger quenching, contrasting sharply with the observation in isolated NCs and confirming the dominance of collective quantum phenomena. Accordingly, the apparent delocalized nature of these cooperative excitons extends the gain lifetime to as long as ∼0.68 ns. This enables the gain coefficient to surpass 1000 cm⁻¹, and facilitates coherent random lasing at an ultralow threshold of 10.3 µJ/cm² under nanosecond optical pumping. Our findings suggest that cooperative excitonics in perovskite superlattices provide a novel route to reconfigure the physical paradigm of optical gain.