De Novo Design of Silicon‐Bridged Molecule Towards a Bipolar Host: All‐Phosphor White Organic Light‐Emitting Devices Exhibiting High Efficiency and Low Efficiency Roll‐Off

A molecular design strategy for a bipolar host material is demonstrated by incorporating both electron donor and electron acceptor into a silicon-bridged structure. A two-color, all phosphor and single-emitting-layer white OLED hosted by the new bipolar compound p-BISiTPA is fabricated. The device displays a high efficiency, with ηc, max of 51.8 cd A−1, ηp, max of 42.7 lm W−1 and ηext, max of 19.1%. Furthermore, the ηext is still as high as 17.4% at the luminance of 1000 cd m−2, with a rather low roll-off value of 8.9%.