Negative-Charge Management Strategy for Both Lifetime Enhancement and Efficiency Roll-Off Suppression in Blue OLEDs

Simultaneously achieving efficient and robust blue organic light-emitting diodes (OLEDs) is a grand challenge, where one of the limitations lies in hole transport materials (HTMs). Here, we unravel the degradation mechanisms of the most promising and widely used HTM, di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane (TAPC). A luminescent defect is discovered in TAPC during degradation in blue OLEDs, which is induced by a two-step electron-induced process. To suppress this degradation, we propose a negative-charge management strategy by introducing a strong electron-withdrawing material, fullerene, at the TAPC interface. This strategy is proven effective in blue phosphorescent OLEDs, resulting in not only a 10-fold enhancement in operational lifetime but also a significant suppression in efficiency roll-off at high brightness over 30 000 cd m–2. Our findings offer a feasible solution to improve the operational stability of blue OLEDs in which the degradation of HTM plays a role, potentially accelerating the commercialization of high-efficiency long-lasting OLED displays.