High‐Lying Triplet Excitons Utilization of Silole Derivatives Enables their Efficiency Breakthrough in OLEDs

Abstract Siloles are routinely studied in the application of organic light‐emitting diodes (OLEDs) due to their high performances of solid‐state fluorescence property and carrier mobility. The structures of siloles used in electroluminescence device reported so far can only utilize singlet excitons, limiting the device efficiency and commercialization. Seeking to build appliable molecular structures to achieve triplet excitons utilization in silole‐core emitters, two derivatives are designed, Silole‐1DPA‐TRZ and Silole‐1Cz‐TRZ , in which electron acceptor of triazine (TRZ) together with electron donors of diphenylamine (DPA) and carbazole (Cz) modified at 1‐position of silole unit form silole‐D‐A structures. This special molecular design, for the first time, enables triplet excitons harvest via high‐lying reverse intersystem crossing (hRISC) process in silole derivatives with hybridized local and charge‐transfer (HLCT) characteristics. Experimental and theoretical studies show that relative to a stronger charge transfer state of Silole‐1Cz‐TRZ , a more equal local excitation/charge transfer distribution in the HLCT state of Silole‐1DPA‐TRZ is realized, making its application in silole‐based OLED with an efficiency breakthrough of ≈9.1% maximum external quantum efficiency (EQE max ).