Tunable Intramolecular Charge Transfer Effect on Diphenylpyrazine-Based Linear Derivatives and Their Expected Performance in Blue Emitters

High efficiency deep-blue emitters are one of the basic requests for an outstanding full-color organic light emitting diode (OLED) display. Herein, a linear D-A-D diphenylpyrazine structure is designed for maximizing the π-conjugation effect, whilst two deep-blue (DPP-DPhC and DPP-D3C) and one blue (DPP-DTPA) fluorophores are synthesized by incorporating the N-phenylcarbazole and triphenylamine donor units, respectively. As a result, they emit bright deep-blue to blue fluorescence with the luminescence quantum yields of 0.312–0.888 in solid state. Fortunately, all the non-doped and doped OLED devices show deep-blue (N-phenylcarbazole disubstituted compounds, DPP-DPhC and DPP-D3C) and blue (triphenylamine derivative, DPP-DTPA) electroluminescence (EL) performance with the maximum external quantum efficiencies (EQEs) of >4%. Comprehensively considering other parameters, the deep-blue non-doped OLED device based on DPP-DPhC exhibits the best EL performance with the maximum EQE of 5.73% with the Commission International de L'Eclairage (CIE_x,y) coordinate of (0.151, 0.078) among them. These results demonstrate the feasibility of this strategy and provide a simple method to achieve high efficiency deep-blue emitters.