Co-deposited copper(I) complexes integrating phosphorescence and TADF properties for highly efficient OLEDs

Abstract

The strategy to co-deposit copper halide and organic materials to directly generate emissive copper complexes is taken into account as a straightforward and promising way to fabricate organic light-emitting diodes (OLEDs) compared with using presynthesized complexes. In this work, four aza-9,9-Spirobifluorenes (aza-SBFs) with the nitrogen atom at different positions of azafluorene moiety were co-deposited with copper(I) iodide (CuI) to form emissive complexes. Intriguingly, we found that the emission properties of these co-deposited copper complexes contain phosphorescent and thermally activated delayed fluorescent (TADF) characteristics. Through changing the position of nitrogen atom, the TADF process can be effectively enhanced, resulting in PLQY up to 92.2 %. Consequently, green OLED with a high current efficiency of 41.9 cd/A, power efficiency of 32.9 lm/W, and external quantum efficiency (EQE) of 16.8 % were achieved by employing the co-deposited copper complex as the emitter.