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

Abstract

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 near-ultraviolet 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.