Affiliation:
1. Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
2. Department of Soft Nanomaterials Nanoscience and Nanotechnology Center The Institute of Scientific and Industrial Research Osaka University 8‐1 Mihogaoka Osaka Ibaraki 567‐0047 Japan
Abstract
AbstractOrganic light‐emitting diodes (OLEDs) employing a single active layer potentially offer a number of benefits compared to multilayer devices; reduced number of materials and deposition steps, potential for solution processing, and reduced operating voltage due to the absence of heterojunctions. However, for single‐layer OLEDs to achieve efficiencies approaching those of multilayer devices, balanced charge transport is a prerequisite. This requirement excludes many efficient emitters based on thermally activated delayed fluorescence (TADF) that exhibit electron trapping, such as the green‐emitting bis(4‐(9,9‐dimethylacridin‐10(9H)‐yl)phenyl)methanone (DMAC‐BP). By employing a recently developed trap‐free large band gap material as a host for DMAC‐BP, nearly balanced charge transport is achieved. The single‐layer OLED reaches an external quantum efficiency (EQE) of 19.6%, which is comparable to the reported EQEs of 18.9–21% for multilayer devices, but achieves a record power efficiency for DMAC‐BP OLEDs of 82 lm W−1, clearly surpassing the reported multilayer power efficiencies of 52.9–59 lm W−1. In addition, the operational stability is greatly improved compared to multilayer devices and the use of conventional host materials in combination with DMAC‐BP as an emitter. Next to the obvious reduction in production costs, single‐layer OLEDs therefore also offer the advantage of reduced energy consumption and enhanced stability.
Subject
Mechanical Engineering,Mechanics of Materials,General Materials Science