Ion Effects on the Performance of the Single‐Layer Organic Light‐Emitting Devices Based on Adding Salt Additives

Abstract

The single‐layer organic light‐emitting devices provide a promising way for low‐cost, large‐area displays. Iridium (III) complex may play an important role to achieve this target due to its unique ionic characteristics. To achieve high‐performance single‐layer devices, blending the salt additives into the active layer is an effective strategy. However, the effects of different cation and anion additives on the device's performance are still unclear. Herein, the single‐layer light‐emitting devices are fabricated by using solution‐processed iridium (III) complex mixed with various molecular salts. It is implied in the results that the improvement of the device luminescence and recombination efficiency is owing to the enhanced carrier injection and improved carrier balance in the emitting layer by the ion‐additive‐induced electrical double layer at the interface. The smaller cation can improve the carrier injection of the device more efficiently due to the stronger ion mobility and the anion with the smaller association coefficient shows a better device performance since the stronger dissociation ability of the ions can lead to a better ion migration ability. In addition, the introduction of poly (methyl methacrylate) into the active film can improve the single‐layer device performances by reducing leak current in bulk.