Diluted exciplex concentrations in organic light emitting diodes for blue-shifted spectra and improved efficiency

Abstract

In this work, the effects of different ratios of the donor/acceptor and spacer host materials on exciplex organic light emitting diode (OLED) based DMAC-DPS:PO-T2T were explored, and an obvious spectral blue-shift and improved efficiency were achieved. It is noted that adjusting the ratios of the donor/acceptor and inserting spacer materials can regulate the distance between exciplex molecules to suppress concentration quenching. As a result, a 30–40 nm blue-shift and a high external quantum efficiency (EQE) of ∼10% were achieved in all OLEDs and the maximum current efficiency, power efficiency and EQE of 35.4 cd A⁻¹, 33.7 lm W⁻¹ and 13.4% were obtained in 70% concentration mCP spacer. The improved exciton utilization derived from multiple reverse intersystem crossing processes and efficient energy transfer were responsible for the high efficiency.