Effect of anode carrier concentration on OLED performance

A study was carried out to understand the effect of carrier concentration in anode on the electroluminescent performance of the OLEDs. A set of indium tin oxide (ITO) films with similar sheet resistance but different carrier concentrations was fabricated by radio frequency magnetron sputtering using a hydrogen-argon gas mixture at a process temperature of ∼60°C. The surface electronic structure of ITO was found to be relevant to the carrier concentration in ITO film, which is crucial for the carrier injection. A set of identical OLEDs was fabricated on ITO films with different carrier concentrations. It is found that the anode contact property at ITO/organic interface can be optimized by controlling ITO bulk carrier concentrations and its surface properties through surface modification. The current density-luminance-voltage characteristics of the devices reveal that the carrier concentration in ITO also plays a role in improving the device performance. The results and findings of this work have provided a technical guidance and fundamental insight for engineering the ITO surface electronic properties that are desired for an efficient and durable OLED.