Solution-processed deep-blue fluorophores based on phenanthroimidazole integrated with benzimidazole with HLCT character for efficient deep-blue organic light emitting devices

Organic light-emitting diodes (OLEDs) has been used extensively in the field of display technology because of their advantageous features for the next-generation displays. However, the development of efficient deep-blue emitters with Commission International de l'Eclairage CIEy < 0.1 is very rare. In this context, we have designed and synthesized two efficient deep blue emitters PTPIBI and m-CF3PIBI by incorporating weak donor phenanthroimidazole (PI) and weak acceptor benzimidazole (BI) to study their potential application in deep-blue organic electronic devices. The systematic investigation of photophysical and theoretical properties of the both the fluorophores indicate that the materials possesses locally excited (LE) and charge transfer (CT) excited states character. The synthesized emitters showed high thermal stability and intense blue emission with high quantum yields. Hence, we have fabricated solution-processed undoped and doped OLED devices with newly synthesized emitters and observed that the PTPIBI demonstrated the superior performance as compared to that of m-CF3PIBI. The best electroluminescent (EL) performance is displayed by the device fabricated with PTPIBI (5 wt% in the Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) host), showing a maximum external quantum efficiency (EQE) of 2.4%, CIE coordinates of (0.15, 0.08) and maximum luminance of 2507 cd/m2.