Effect of the Glass Transition Temperature of Organic Materials on Exciton Recombination Region of Deep Blue OLED under Thermal Stress

Abstract

The carrier transport and the exciton recombination region, which are strongly affected by temperature, are essential to organic light‐emitting diodes (OLEDs) under thermal stress. A different charge carrier transport materials with different glass transition temperature (Tg) is selected to investigate their effect on the thermal stability of OLEDs. By calculating the carrier mobility at different annealing temperatures and comparing the simulated values by the Arrhenius equation, the effect of the thermal stress on the performance of OLEDs is analyzed. Then, using the luminescent dye as a probe adjacent to the emitting layer and charge transporting layer to identify the exciton recombination region at different temperatures and driving voltages, it is revealed that replacing the functional material with low Tg with a high Tg one could effectively increase the thermal stability of the device to 100 °C. The optimized devices have a reduced turn‐on voltage, and the electron mobility is increased by more than one order of magnitude, which was conducive to exciton recombination. The work promotes the application of OLEDs in extreme environments by improving their thermal stability.