Synthesis and properties of wide bandgap polymers based on tetraphenylsilane and their applications as hosts in electrophosphorescent devices

Abstract

Wide bandgap materials are important in the organic optoelectronic field. In this study, a diphenylphosphine oxide-functionalized tetraphenylsilane moiety was designed and applied in the construction of wide bandgap materials. The wide bandgap polymer PFSCPO was synthesized via a Suzuki coupling reaction between diphenylphosphine oxide substituted tetraphenylsilane and carbazole modified dihexylfluorene. PFSC without the diphenylphosphine oxide group was also prepared for comparison. They both show high thermal stabilities and good morphological stabilities. Doped films using these two polymers as hosts and Ir(ppy)₃ as a guest were prepared via the spin-coating method. Compared with PFSC, the diphenylphosphine oxide group with strong electron-withdrawing property decreased the LUMO energy level of PFSCPO and facilitated electron injection in OLEDs. The turn-on voltage was 7.5 V in the PFSC/Ir(ppy)₃ doped device, which reduced to 6.3 V in the PFSCPO/Ir(ppy)₃ doped device. The maximum current efficiency also increased from 8.83 cd A⁻¹ to 9.33 cd A⁻¹.