In Situ Substrate Temperature Control for High-Performance Blue-Emitting OLEDs with Extended Operational Lifetime.

Abstract

Organic light-emitting diodes (OLEDs) are currently a leading technology in display applications, providing superior optoelectrical performance and image quality compared to other sources. A challenge in OLEDs is prolonging the operational lifetime of blue pixels to achieve nearly 100% internal quantum efficiency, comparable to red and green pixels. Recently, there has been growing interest in controlling the molecular orientation in the emitting layer (EML) to enhance the optoelectrical performance of OLEDs and address this issue. A low driving current at a specific luminance allows OLEDs to significantly enhance their operational lifetime under constant current and efficiency. In this study, the investigation focused on whether substrate temperature (T_sub) predominantly influences the orientation of the host molecules in the EML. A low T_sub significantly enhances the hole mobility of the EML, enabling recombination inside the EML. As a result, it was observed that blue-emitting OLEDs using this technique significantly increase the operational lifetime by approximately 6.6 times when T_sub is -4 °C compared to 40 °C of T_sub, eliminating the material deformation of a weak organic layer.