Tuning the emission spectrum of highly stable cesium lead halide perovskite nanocrystals through poly(lactic acid)-assisted anion-exchange reactions

We demonstrate an organic macromolecule-assisted anion-exchange reaction method for tuning the emission spectrum of cesium lead halide perovskite (CsPbX3) nanocrystals (NCs) from green to nearultraviolet using a microreactor. Using poly(lactic acid) (PLA), the emission peak of CsPbX3 NCs can be tuned from 514 nm to 420 nm while maintaining high photoluminescence (PL) quantum yields (QYs) of 33-90%. By taking advantage of the microreactor, we synthesize parent CsPbBr3 NCs and complete anion-exchange reactions at the same time, which is more efficient than most previously reported methods. The stability of CsPbX3 NCs is improved by PLA coating, especially for CsPbCl3, which shows long-term stability under ambient conditions for at least two weeks. The CsPbBr3 NCs are utilized with a red phosphor on a blue light emitting-diode (LED) chip, achieving white light emission with a luminous efficacy of 62.93 lm W-1 under a 20 mA driving current. Highly efficient white LEDs (wLEDs) demonstrate the potential of halide perovskite NCs for optoelectronic applications, including low-cost displays, lighting, and optical communication.