Efficient deep-blue non-doped organic light-emitting diode with improved roll-off of efficiency based on hybrid local and charge-transfer excited stateElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra15079a

High-efficiency deep-blue light-emitting materials are of significance in the fields of commercial full-color displays and solid-state lightings. A hybrid local and charge-transfer (HLCT) excited state not only favors deep-blue emission avoiding a large redshift from a strong charge-transfer (CT) state, but also simultaneously harvests both high photoluminescence efficiency and high exciton-utilizing efficiency. Herein, we report a new V-shaped acceptor-donor-acceptor (A-D-A) type molecule TPA-2PPI with an HLCT emissive state, which is modified from D-A type TPA-PPI. The non-doped device based on the TPA-2PPI emitter still exhibits deep-blue emission peaking at 452 nm with a full width at half maximum (FWHM) of only 50 nm and Commission International de L'Eclairage (CIE) coordinates of (0.151, 0.108). Compared with TPA-PPI, the electroluminescence (EL) not only maintains high efficiency with a maximum external quantum efficiency (EQE) of 4.91%, but also the EL device displays a significantly slower roll-off of efficiency at high luminances with an EQE of 4.89% (or 4.56%) at 100 cd m −2 (or 1000 cd m −2 ), which is confidently beneficial for the operative stability of OLED devices. Acceptor-donor-acceptor triphenylamine-phenanthroimidazole derivate (TPA-2PPI) servers as an emitter, whose device exhibits deep-blue emission, high efficiency and slow roll-off of efficiency.