Ultra-broadband light-emitting diodes from co-evaporated lead-free CsCu2I3

Abstract

• CsCu 2 I 3 films were prepared by vacuum co-evaporation method. • Co-evaporated CsCu 2 I 3 film exhibits self-trapped exciton behavior. • LEDs using the CsCu 2 I 3 films show red-shifted and ultra-broad EL. As an alternative to the conventional solution-processing, a vacuum co-evaporation method is developed to prepare CsCu 2 I 3 thin film, for fabricating light-emitting diodes (LEDs). LEDs using the co-evaporated lead-free CsCu 2 I 3 films exhibit ultra-broad warm-white emission. We found that the LEDs using the CsCu 2 I 3 thin films have red-shift and broadened electroluminescence (EL) with a full width at half-maximum of 245 nm in contrast to 132 nm from photoluminescence (PL) spectra for the CsCu 2 I 3 films. The current hysteresis of LEDs using the CsCu 2 I 3 films indicates that the migration of ions provides a new radiative-recombination center and further resulting in EL change and broadening. The experimental work presented here gains insight on broadening EL spectra for the LEDs with self-trapped exciton materials.