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

Abstract 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.