Initial exploration of solution-processed ultrapure blue organic light emitting diodes utilizing phosphorescent Pt complex and MR-TADF emitters

Abstract

To achieve very high efficiency in solution-processed organic light emitting diodes (OLEDs), one promising and trailblazing approach is the utilization of the phosphor sensitized fluorescence (PSF) mechanism. In our study, we successfully apply this mechanism to fabricate highly efficient blue solution-processed device by introducing novel structured platinum (Pt) complex as a phosphorescent sensitizer. The significant spectral overlap between the sensitizer and final dopant (J_F), with a J_F value of 14.83 × 10¹⁴ nm⁴ M⁻¹ cm⁻¹, enables high rates of energy transfer and results in a moderately high external quantum efficiency, with the device displaying (0.12, 0.12) color coordinates while achieving a notable 9.68 % external quantum efficiency. The system is particularly promising for designing OLEDs with sub-microsecond radiation decay times. Additionally, the PSF emitter exhibits ultrapure blue emission, with a narrow full-width half maximum of 16 nm from photoluminescence and 18 nm from electroluminescence. Moreover, the radial distributions of EML molecules at different annealing temperatures were investigated, showing the absence of molecular aggregation, ensuring a smooth surface for the solution device. These findings highlight the promising potential of employing the PSF mechanism along with a stable interfacial layer to achieve remarkable performance in solution-processed OLED devices.