Cyanophenyl spiro[acridine-9,9′-fluorene]s as simple structured hybridized local and charge-transfer-based ultra-deep blue emitters for highly efficient non-doped electroluminescent devices (CIEy ≤ 0.05)

Abstract

The hybridized local and charge-transfer (HLCT) excited state is a successful approach to accomplish both high external and internal quantum efficiency. To obtain deep blue emissive HLCT emitters, two cyanophenyl substituted spiro[acridine-9,9′-fluorene] isomers, namely SAFmCN and SAFpCN, were designed and synthesized. The photophysical and density functional theory (DFT) results confirmed that both molecules exhibited HLCT features with strong ultra-deep blue emissions in both solution and film states with emission peaks at 410–433 nm. The non-doped OLED devices showed emissions in high-definition television (HDTV) standard blue color (CIEy ≤ 0.05) with a narrow full width at half maximum (50–56 nm), excellent electroluminescence (EL) performance and a low turn-on voltage of 3.2 V. Particularly, the SAFpCN-based device achieved a maximum luminance efficiency (CE) and maximum external quantum efficiency (EQE) of 6.54 cd A⁻¹ and 4.63%, respectively.