Abstract
High triplet energy level and thermal stability are crucial properties for host materials to fulfill organic light-emitting devices (OLEDs) with great performance. In this work, four π-shape bipolar host materials, GHA1-4 were designed and synthesized using dibenzofuran core. These hosts exhibit high triplet energy levels as well as excellent thermal stability. Green top-emission OLEDs with GHA1-4 as hosts and Ir (ppy)3 as emitter exhibited excellent performance with high external quantum efficiency (EQEmax) values of above 40%. In addition, devices incorporating GHA1 and GHA3 exhibit a low turn on voltage of 2.07 V, EQEmax of 45.0% and long LT95 device lifetime of 184 h, as well as remarkably small roll-off of only 2.5% at the brightness of 10,000 cd/m2.
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