Efficient near-ultraviolet (NUV) electroluminescence based on a benzonitrile acceptor HLCT material with balanced carrier mobilities and high color purity

Abstract

Balanced carrier injection/transport and high color purity are critical for highly efficient near-ultraviolet (NUV) electroluminescence (EL) emitters. Herein, two novel structurally simple NUV donor–π–acceptor (D–π–A) molecules, namely CZ-PPCN and TPA-PPCN, with a benzene π-bridge containing carbazole/triphenylamine as donors and benzonitrile as the acceptor were designed and synthesized, and they exhibited hybrid local charge transfer (HLCT) characteristics. The introduction of the benzonitrile group of the CZ-PPCN molecule not only enhances charge carrier injection but also promotes hole and electron mobility balance through the formation of supramolecular hydrogen bonds (both up to 10⁻⁵ cm² V⁻¹ s⁻¹). The non-doped and doped devices fabricated using CZ-PPCN exhibit the best excellent EL performances. As a result, the non-doped device of the CZ-PPCN emitter exhibits a high maximum external quantum efficiency (EQE_max) of 6.42%, and the device exhibits deep-blue emission with Commission International de L'Eclairage (CIE) coordinates of (0.154, 0.075). More importantly, the CZ-PPCN-based doped device exhibits EL emission peaks at 405 nm with CIE coordinates of (0.159, 0.040), while still retaining a high EQE of 7.14%. This work provides a simple design strategy for advancing next-generation NUV emitters with balanced carrier mobility and superior color purity.