Ternary Exciplexes for High Efficiency Organic Light-Emitting Diodes by Self-Energy Transfer

Ternary exciplexes with an external quantum efficiency of 17.5% are developed by mixing a p-type donor material, an n-type acceptor material, and a donor-acceptor type material together. In the ternary mixture, the n-type donor generates exciplexes with the p-type donor and the donor-acceptor type material at the same time. Two different exciplexes with dissimilar emission wavelengths are formed and the emission of the high-energy exciplex is transferred to the low-energy exciplex by energy transfer. The high-energy exciplex and low-energy exciplex work as a host and dopant in the emitting layer, respectively. The internal exciplex-to-exciplex energy transfer induces efficient emission of the low-energy exciplex, resulting in high efficiency of 17.5% in the exciplex device. This is the first demonstration of self-energy transfer in the exciplex and the efficiency of the ternary exciplexes is one of the best quantum efficiencies achieved in the exciplex organic light-emitting diodes.