Tuning hole transport layers and optimizing perovskite films thickness for high efficiency CsPbBr3 nanocrystals electroluminescence light-emitting diodes

Abstract

Metal halide perovskite nanocrystals (NCs) have sparked considerable attentions in the area of light-emitting diodes (LED) by virtue of their remarkable color purity and spectral tunability (400–700 nm). However, the optoelectronic performance of LED devices based on perovskite NCs is severely limited by the problem of charge injection since (i) the charge injection layers exhibit significant differences in energy levels and charge mobility, (ii) one thick NCs emitting layer can obstruct the electrons transmission and one thin NCs emitting layer can change the charge recombination region, inducing series of troubles in fabrication and application of LED devices. Herein, a series of LED devices based on cesium lead bromide (CsPbBr3) green-emitting perovskite NCs are reported by adopting Poly-N-vinylcarbazole (PVK)/Poly [9,9-dioctylfluoreneco-N-[4-(3-methylpropyl)]diphenylamine] (TFB) and Poly[bis(4-phenyl) (2,4,6-trimethylphenyl)amine] (PTAA) as the hole transport layer (HTL) materials. With the increase of applied voltage, the CsPbBr3 NCs LED device with PTAA as HTL displays better transport characteristics, such as a lower turn-on voltage and a higher luminance, than that of the device with TFB and PVK as HTL. By optimizing the spin-coating craft parameter of the CsPbBr3 NCs layer, an efficient green-emitting CsPbBr3 NCs LED device with maximum luminance of 4531 cd m−2, current efficiency of 14.4 cd A−1, power efficiency of 14.1 lm W−1 and maximum external quantum efficiency of 4.28% was obtained. These results provide an approach for the practical applications of CsPbBr3 NCs electroluminescence LED devices.