Efficient doped and non-doped OLED based on a deep-blue HLCT material and all-HLCT WOLED with standard white-light emission

Abstract

Hybrid local and charge transfer (HLCT) materials are attracting considerable interest in organic light-emitting diodes (OLEDs) owing to their advantages such as 100% theoretical internal quantum efficiency and low efficiency roll-off, particularly for blue HLCT materials. Although progress has been made toward high-efficient HLCT materials and even HLCT-based white OLEDs (WOLEDs), all-HLCT WOLEDs remain rarely reported. In this work, we report two novel HLCT molecules: blue CzPyPPI based of the phenanthroimidazole (PPI) and orange BTPA4 based of the benzothiadiazole, and the HLCT characteristics were revealed through theoretical calculations and photophysical properties. The CzPyPPI and BTPA4 neat films exhibited photoluminescence quantum yields as high as 72.0% and 89.8%, respectively, contributing to high device performances. The doped device based on CzPyPPI delivered a maximum external quantum efficiency (EQEmax) of 7.37% with deep blue emission (CIEy = 0.063), while the doped device based on BTPA4 showed an EQEmax of 5.13%. Importantly, WOLEDs with a simple emissive layer consisting of the blue CzPyPPI host and orange BTPA4 dopant were fabricated. The optimized WOLED presented an EQEmax of 6.86% with low efficiency roll-off, together with near-standard white light emission with CIE coordinates of (0.335, 0.334). This work provides new insights for the development of high-performance blue HLCT materials and all-HLCT WOLEDs.