Stable All‐Fluorescence White Organic Light‐Emitting Diodes with High Efficiency and High CRI

Abstract

White organic light‐emitting diodes (WOLEDs) have been regarded as the candidates for next‐generation flat‐panel displays and solid‐state lighting due to their low cost. However, it is still challenging to achieve two‐component WOLEDs with high efficiency, high color index (CRI), and long lifetime. Here, high‐performance all‐fluorescence WOLEDs based on a blue fluorescent emitter and an orange thermally activated delayed fluorescent (TADF) emitter are demonstrated. The optimized all‐fluorescence WOLED with two EMLs presents the maximum external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 23.4%, 40.2 cd A−1, and 33.2 lm W−1, corresponding to a maximum CRI value of 83.1 and Commission Internationale de L'Eclairage (CIE) coordinate of (0.30, 0.31). To further improve the device stability, the all‐fluorescence WOLEDs with three EMLs and tandem structure are constructed, respectively. Under the premise of ensuring efficiency, in going from the two‐EMLs to the three‐EMLs and the tandem structure, the LT50 (time to 50% of the initial luminance) of all‐fluorescence WOLEDs increase from 601 to 714 h and 1622 h at an initial luminance of 1000 cd m−2. These strategies and results present new insight into the design of all‐fluorescence WOLEDs with high efficiency, high CRI, and extended lifetime.