Color-Tunable Boron-Based Emitters Exhibiting Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence for Efficient Solution-Processable Nondoped Deep-Blue to Sky-Blue OLEDs

Abstract

Three new color-tunable (deep-blue to sky-blue) and solution-processable emitters-9 '-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-9 ' H-9,3 ':6 ',9 ''-tercarbazole (TB-3Cz), 9 '-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-9,9 ''-diphenyl-9H,9 ' H,9 '' H-3,3 ':6 ',3 ''-tercarbazole (TB-P3Cz), and 9-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-N-3,N-3,N-6,N-6-tetraphenyl-9H-carbazole-3,6-diamine (TB-DACz)-are demonstrated, which are cleverly designed and synthesized by appending a boron-fused entity as an electron acceptor to different electron-rich entities containing carbazole derivatives as donors. The thermal, photophysical, electrochemical, and electroluminescent characteristics of all the new materials are extensively investigated. Comprehensive photophysical investigations reveal that these emitters exhibit not only thermally activated delayed fluorescence (TADF) but also aggregation-induced emission (AIE) properties. Consequently, solution-processable organic light-emitting diodes (OLEDs) fabricated using these new materials as nondoped emitters in the emissive layer exhibit a maximum external quantum efficiency (EQE) and Commission Internationale de l'eclairage (CIE) color coordinates of 9.90% and (0.17, 0.07), respectively, for TB-3Cz; 6.13% and (0.15, 0.08), respectively, for TB-P3Cz; and 6.04% and (0.18, 0.40), respectively, for TB-DACz. As far as it is known, the performance and ultrahigh color purity satisfying the deep-blue CIE coordinates of the National Television System Committee (NTSC) for TB-3Cz and TB-P3Cz are the highest reported thus far for nondoped solution-processable TADF emitters, indicating the great potential of these materials as deep-blue luminogens in OLED applications.