Electric-Field-Regulated Energy Transfer in Chiral Liquid Crystals for Enhancing Upconverted Circularly Polarized Luminescence through Steering the Photonic Bandgap.

Yang, Xuefeng; Zhou, Minghao; Wang, Yafei; Duan, Pengfei · Adv Mater · 2020

basic_science · Level V

Where this comes from

Abstract

Circularly polarized luminescent materials with high dissymmetry factor (g<sub>lum</sub> ) have been attracting increasing attention due to their distinctive photonic properties. In this work, by incorporating upconversion nanoparticles (UCNPs) and CsPbBr<sub>3</sub> perovskite nanocrystals (PKNCs) into a chiral nematic liquid crystal (N*LC), enhanced upconverted circularly polarized luminescence (UC-CPL) based on a radiative energy transfer (RET) process from UCNPs to CsPbBr<sub>3</sub> PKNCs is successfully implemented. By locating the emission peak of CsPbBr<sub>3</sub> PKNCs at the center of the photonic bandgap of N*LC, the maximum g<sub>lum</sub> value of UC-CPL can be amplified to an extremely large value of 1.1. Meanwhile, upconverted emission of UCNPs can be significantly enhanced due to the band edge enhancement effect of the N*LC, subsequently enhancing the emission of the CsPbBr<sub>3</sub> PKNCs through the RET process. In addition, an applied electric field can switch the upconverted emission of the UCNPs, as well as the RET process, enabling an electric-field-controlled UC-CPL switch.