Enabling high-efficiency organic light-emitting diodes with a cross-linkable electron confining hole transporting material

•Design, synthesis, and characterization of a thermally cross-linkable hole transporting material VPEC.•The resulting VPEC material shows a hole mobility of 1 × 10−4 cm2 V−1 s−1 and a triplet energy of 2.88 eV.•Hole transporting material also shows effective electron confining function with LUMO energy level of –2.0 eV.•The resulting solution process red, green and blue (RGB) OLED devices show high efficiency at higher luminance.

Wet-process enables flexible, large area-size organic devices to be fabricated cost-effectively via roll-to-roll manufacturing. However, wet-processed devices often show comparatively poor performance due to the lack of solution-process feasible functional materials that exhibit robust mechanical properties. We demonstrate here a cross-linkable material, 3,6-bis(4-vinylphenyl)-9-ethylcarbazole (VPEC), to facilitate the injection of hole and meanwhile effectively confine electron to realize, for examples, high efficiency organic light-emitting diodes, especially at high luminance. The VPEC shows a hole mobility of 1 × 10−4 cm2 V−1 s−1 and a triplet energy of 2.88 eV. Most importantly, the VPEC not only works for devices containing low band-gap red or green emitters, but also for the counterpart with high band-gap blue emitter. With the electron confining hole transporting material, the power efficiency of a studied red device, at 1,000 cd m−2 for example, is increased from 8.5 to 13.5 lm W−1, an increment of 59%, and the maximum luminance enhanced from 13,000 to 19,000 cd m−2, an increment of 46%. For a high triplet energy blue emitter containing device, it is increased from 6.9 to 8.9 lm W−1, an increment of 29%, and the maximum luminance enhanced from 9,000 to 11,000 cd m−2, an increment of 22%.

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