Negative-Charge\nManagement Strategy for Both Lifetime\nEnhancement and Efficiency Roll-Off Suppression in Blue OLEDs

Simultaneously achieving\nefficient and robust blue organic light-emitting\ndiodes (OLEDs) is a grand challenge, where one of the limitations\nlies in hole transport materials (HTMs). Here, we unravel the degradation\nmechanisms of the most promising and widely used HTM, di-[4-(<i>N</i>,<i>N</i>-di-<i>p</i>-tolyl-amino)-phenyl]cyclohexane\n(TAPC). A luminescent defect is discovered in TAPC during degradation\nin blue OLEDs, which is induced by a two-step electron-induced process.\nTo suppress this degradation, we propose a negative-charge management\nstrategy by introducing a strong electron-withdrawing material, fullerene,\nat the TAPC interface. This strategy is proven effective in blue phosphorescent\nOLEDs, resulting in not only a 10-fold enhancement in operational\nlifetime but also a significant suppression in efficiency roll-off\nat high brightness over 30 000 cd m<sup>–2</sup>. Our\nfindings offer a feasible solution to improve the operational stability\nof blue OLEDs in which the degradation of HTM plays a role, potentially\naccelerating the commercialization of high-efficiency long-lasting\nOLED displays.