Room-Temperature Treatment with Thioacetamide Yielding Blue- and Green-Emitting CsPbX3 Perovskite Nanocrystals with Enhanced Photoluminescence Efficiency and Stability

While multiple protocols are currently available for obtaining green- and red-emitting lead halide perovskite nanocrystals (NCs) with near-unity photoluminescence quantum yield (PLQY), achieving this target for the blue-emitting NCs is still quite challenging. This is an impediment to the development of perovskite-based highly efficient white LEDs of which blue is an essential component. Herein, we show that room-temperature treatment of the blue-emitting CsPbCl1.5Br1.5, cyan-emitting CsPbClBr2 and green-emitting CsPbBr3 NCs with thioacetamide not only enhances the PLQY to near-unity (similar to 97-99%) without affecting the PL maximum and bandwidth, but also improves the stability of the systems significantly. The investigation reveals that effective passivation of under-coordinated surface Pb2+ through formation of Pb-S and Pb-NH2 bonds and removal of excess lead atoms suppress the nonradiative recombination channels and enhances the PLQY and stability of the NCs. Outstanding PL efficiency and superior long-term stability make these systems potential ingredients for various lighting and display applications.