Purely organic phosphor sensitization for efficiency improvement in yellow fluorescent organic light-emitting diodes

Abstract

Utilization of a purely organic based room-temperature phosphorescent (RTPH) emitter as a sensitizer was studied by employing it in yellow fluorescent organic light-emitting diodes (OLEDs). The RTPH sensitizer can harvest radiative triplet excitons and would transfer them to the yellow fluorescent dopant for efficient fluorescence, just like a conventional phosphorescent sensitizer. The selected RTPH material was 3-(9H-carbazol-9-yl)-10-(p-tolyl)-10H-phenoselenazine (PSez9Cz), which emits at 507 nm by phosphorescence, and the fluorescent dopant was 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb). The maximum external quantum efficiency of the yellow fluorescent OLEDs was increased from 2.8% to 8.1% by co-doping 10 wt% of RTPH sensitizer and 0.8 wt% of fluorescent dopant due to efficient Förster energy transfer from the RTPH sensitizer to the dopant.