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 eta(c, max) of 51.8 cd A(-1) eta(p, max) of 42.7 lm W-1 and eta(ext, max) of 19.1%. Furthermore, the eta(ext) 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%.