Thermally cross-linkable hole transporting polymer synthesized by living anionic polymerization for effective electron blocking and reduction of exciton quenching in multilayer polymer light emitting diodes

A new cross-linkable polymer (d-PBAB), which has triphenylamine as the hole transporting moiety and ethynyl group as the thermal cross-linker, was synthesized by a living anionic polymerization and deprotection process. The thermally cross-linked d-PBAB layer had a smooth surface and excellent solvent resistance. The PLED fabricated with cross-linked d-PBAB as hole transporting layer (HTL) showed approximately one and half times higher luminance and four times higher luminous efficiency than those obtained from PLED with PEDOT:PSS. This is ascribed to better abilities of cross-linked d-PBAB to block electrons and prevent exciton quenching than those of PEDOT: PSS at the emitting layer (EML) interface. These results strongly suggested that cross-linked d-PBAB can be a promising material to replace conventional PEDOT:PSS.