A solution-processed trilayer electrochemical device: Localizing the light emission for optimized performance

We present a solution-processed trilayer light-emitting device architecture, comprising two hydrophobic and mobile-ion-containing "transport layers" sandwiching a hydrophilic and ion-free "intermediate layer", which allows for lowered self-absorption, minimized electrode quenching, and tunable light emission. Our results reveal that the transport layers can be doped in situ when a voltage is applied, that the intermediate layer as desired can contribute significantly to the light emission, and that the key to a successful operation is the employment of a porous and (∼5-10 nm) thin intermediate layer allowing for facile ion transport. We report that such a solution-processed device, comprising a thick trilayer material (∼250 nm) and air-stable electrodes, emits blue light (λ _peak = 450, 484 nm) with high efficiency (5.3 cd/A) at a low drive voltage of 5 V.