LAUSR

Reducing the excitation threshold to minimize the Joule heating is critical for the realization of perovskite laser diodes. Although bound excitons are promising for low threshold laser, how to generate them at room temperature for laser applications is still unclear in quasi‐2D perovskite‐based devices. In this work, via engineering quasi‐2D perovskite PEA2(CH3NH3)n‐1PbnBr3n+1 microscopic grains by the anti‐solvent method, room‐temperature multiexciton radiative recombination is successfully demonstrated at a remarkably low pump density of 0.97 µJ cm−2, which is only one‐fourth of that required in 2D CdSe nanosheets. In addition, the well‐defined translational momentum in quasi‐2D perovskite grains can restrict the Auger recombination which is detrimental to radiative emission. Furthermore, the quasi‐2D perovskite grains are favorable for increasing binding energies of excitons and biexcitons and so as the related radiative recombination. Consequently, the prepared phase quasi‐2D perovskite film renders a threshold of room‐temperature stimulated emission as low as 13.7 µJ cm−2, reduced by 58.6% relative to the amorphous counterpart with larger grains. The findings in this work are expected to facilitate the development of solution‐processable perovskite multiexcitonic laser diodes.