Rational design of hybridized local and charge transfer emitters towards deep blue emission by incorporating extra cyano-based acceptor moieties

Abstract

Hybridized local and charge transfer (HLCT) molecules have garnered considerable attention for their potential to fully utilize excitons and achieve efficient blue luminescence. Here, we proposed a molecular design strategy of excited state manipulation from locally excited (LE) to HLCT via introducing cyano groups. 3ph-phCz and 2(3ph)-phCz without cyano groups are mainly composed of LE components, while 3PhCN-PhCz and 2(3phCN)-phCz are composed of HLCT components and have a deep highest occupied molecular orbital energy level. Analysis of their photophysical properties revealed that the incorporation of the cyano group enhanced the photoluminescence quantum yield of the molecule from 20% to 100% in solution. Non-doped solution-processed 2(3phCN)-phCz based devices achieved a maximum external quantum efficiency of 4.43% and an emission peak at 438 nm, which provides a promising avenue for developing HLCT blue materials. Furthermore, a maximum external quantum efficiency of 17.34% with a maximum current efficiency of 55.67 cd A⁻¹ is obtained for doped devices using 2(3phCN)-phCz as the host.