Solution-processed orange and white OLEDs sensitized by an electroactive pure organic room-temperature phosphorescent polymer

Abstract

Phosphorescence-sensitized fluorescence (PSF) shows great potential for overcoming the 25% internal quantum efficiency limit for fluorescent OLEDs. Other than vacuum thermal deposition, herein we report solution-processed PSF. As a proof of concept, an electroactive pure organic room-temperature phosphorescence (RTP) polymer with sky-blue emission is selected as the sensitizer of the conventional orange fluorescent emitter. Due to the improved exciton utilization, the resultant sensitized device realizes a bright orange electroluminance with a peak external quantum efficiency (EQE) of 6.1% (17.9 cd A⁻¹, 11.0 lm W⁻¹) and Commission Internationale de L’Eclairage (CIE) coordinates of (0.42, 0.47). By optimizing the doping concentration of the fluorescent emitter, furthermore, a spectrally stable white light is also achieved, revealing a maximum EQE of 7.4% (19.3 cd A⁻¹, 12.0 lm W⁻¹) together with CIE coordinates of (0.30, 0.43). The results clearly indicate that solution-processed PSF based on an RTP polymer is a promising approach towards efficient fluorescent OLEDs.