Benzothiadiazole based “hot exciton’’ materials for red electroluminescence with the maximum external quantum efficiency approaching 10%

Abstract

To achieve high exciton utilization of organic light-emitting diodes, the construction of donor–acceptor (D–A) molecules with a “hot exciton” feature has been proved to be an effective strategy. Herein, two novel benzothiadiazole based D–A–D′ type “hot exciton” materials, TPA-BT-PBI and TPA-BT-IM, have been designed and synthesized for red OLEDs. The TPA-BT-PBI and TPA-BT-IM based non-doped devices exhibit maximum external quantum efficiency (EQE_max) values of 2.78% and 5.11%, respectively. The EQE_max of TPA-BT-PBI and TPA-BT-IM based doped devices increased significantly up to 7.78% and 9.41%, respectively. The experimental results demonstrate that the D–A fragment determines its optical properties and incorporating the D′ group is important to improve charge transfer balance and realize high brightness.