Reduced optically pumped amplified spontaneous emission threshold of BUBD-1 thin films by thermally activated delayed fluorescent materials

Abstract

We demonstrated the optically pumped amplified spontaneous emission (ASE) characteristics of a sky-blue fluorescent material (BUBD-1) blending with the thermally activated delayed fluorescence molecule DMAC-DPS and the commonly used host molecule CBP. The photoluminescence quantum efficiency (PLQE) is found to be more than 80% in both of blend films with an optimal concentration. The blending films exhibit the lowest ASE threshold of 1.51 μJ/pulse (CBP: 2 wt%BUBD-1) and 1.19 μJ/pulse (DMAC-DPS: 2 wt%BUBD-1), which are reduced by 84.7% and 87.1%, respectively, compared with that of BUBD-1 neat film. The transient photoluminescence decay curves with varying temperature indicate that the up-conversion through reverse intersystem crossing (RISC) happens in the DMAC-DPS: 2 wt%BUBD-1 blend films. The reduction of ASE threshold in the DMAC-DPS doped blend films may be ascribed to a higher energy transfer efficiency caused by both prompt and delayed Förster energy transfer. This study shows that TADF materials have great potential in reducing the ASE threshold of organic laser materials.