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 (CIE ≤ 0.05)

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 (CIE y ≤ 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. Cyanophenyl substituted spiro[acridine-9,9′-fluorene]s featured with HLCT excited states yielded highly efficient non-doped OLEDs with emissions in high-definition television standard blue color, CIE y ≤ 0.05, and CE max /EQE max of 6.54 cd A −1 /4.63%.