Solution-based green amplified spontaneous emission from colloidal perovskite nanocrystals exhibiting high stability

Solution-based optical amplification affords a host of benefits ranging from flexibility in the choice of cavity size and shape to high photostability afforded by the constant replenishment of gain media. Works reporting solution-based optical amplification in colloidal semiconductor nanocrystals, however, remain sparse due to the difficulty in achieving high particle number densities required for sustained optical gain. In this work, we demonstrate highly stable amplified spontaneous emission (ASE) from a solution of green-emitting CsPbBr3 perovskite nanocrystals dispersed in a nonpolar solvent after a facile postsynthesis processing step. This processing step not only allows for the purification of nanocrystals from their growth solution, but also allows for long-term colloidal stability at high particle concentrations. Although it is widely reported that perovskite nanocrystals suffer from poor chemical stability, our nanocrystal solutions retain their ASE properties despite long-term storage in excess of five months under ambient conditions. Photostability tests show steady ASE intensities in excess of three hours under constant photoexcitation from a femtosecond pulsed laser beam (>107 shots), far exceeding those of thin films by an order of magnitude. This work opens the possibility of harnessing colloidal CsPbBr3 nanocrystals as highly robust, solution-based optical gain media.