[1,2,4]Triazolo[1,5-a]pyridine as regulating unit with high horizontal orientation for efficient non-doped blue OLEDs with negligible efficiency roll-off

Abundant efforts have been devoted to improving the efficiency of organic light-emitting diodes (OLEDs), however, approaches to control the device efficiency roll-off are still extremely limited, especially in non-doped blue OLEDs. In this work, three blue emitters (TAT, TAMT and TAMT-CN) with "hot exciton" properties are designed and synthesized based on [1,2,4]triazolo[1,5-a]pyridine (TP) as a regulating unit as well as anthracene-triphenylamine (An-TPA) as the chromophore. By adjusting the linkage mode and modifying the TP unit, the excited state properties, carrier transfer abilities, horizontal orientation, and device efficiency roll-off were precisely controlled. Among these materials, emitters that directly connect the fused TP unit exhibit balanced charge-transporting ability, higher photoluminescent quantum yield and improved horizontal orientation, resulting in better electroluminescence (EL) performance in non-doped blue OLEDs. As a result, non-doped blue OLEDs exhibit excellent performance with external quantum efficiencies of over 6 %, brightness of over 30,000 cd/m² and EL peaks of around 476 nm. More importantly, the device based on TAMT-CN exhibits an ultra-low efficiency roll-off of 2.97 % at a high brightness of 10,000 cd/m². The accessible molecular unit and feasible design strategy in this work are of great significance for designing highly efficient and ultra-low efficiency roll-off non-doped blue OLEDs. © 2025 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.