Narrowband, angle-independent and efficient polaritonic OLEDs based on TADF emitters

Thin-film interference has traditionally posed a challenge for OLED design, and careful optimization of layer thickness and position is important to achieve efficient light-extraction. However, the unique properties of organic materials—in particular their high oscillator strength and well-defined absorption bands—also facilitate the design of a type of thin-film interference in which strong exciton-photon coupling plays a crucial role. This provides additional tuning parameters and thus allows to achieve device properties not achievable in conventional thin-film architectures. We studied how this emerging design principle can be applied to obtain OLEDs that combine highly saturated, narrowband emission with very good color-stability across all angles of observation, addresses a main challenge that OLEDs face to meet the BT.2020 display standard. We show examples of these polariton OLEDs with red, green and blue emission, and by using TADF and doped transport layers, we demonstrate dramatically improved efficiency, reaching over 20% EQE.