Stable pure-blue hyperfluorescence OLEDs

Abstract

Organic light-emitting diodes (OLEDs) are a promising light-emitting technology useful for various display applications. Despite great progress in this field, there is an ongoing challenge to realize high-performance blue OLEDs with efficiency, good color purity, and device lifetime. Here, we report pure-blue (CIEx,y color coordinates of [0.13, 0.16]) OLEDs with high-efficiency (external quantum efficiency of 32 % at 1000 cd m–2), narrow-emission (full-width half maximum of 19 nm), and good stability (LT95 of 18 hours at an initial luminance of 1000 cd m–2). The design is based on a two-unit stacked tandem hyperfluorescence (HF)-OLED with an improved singlet-excited energy transfer process from a sky-blue TADF assistant dopant (AD) (HDT-1) to a pure-blue terminal emitter (TE) (v-DABNA). Furthermore, the effect of the dopant concentration of terminal emitter on the device performance of hyperfluorescence OLEDs is studied. The device shows a better color purity when dopant concentration is increased. On the other hand, new hyperfluorescence OLEDs are fabricated, in which v-DABNA is replaced by DABNA-2 and dopant concentration is kept to be 0.5 %. Such device shows a lengthened device stability of LT95 of 26 h at an initial luminance of 1000 cd m-2