Temperature dependence of the driving properties for a green thermally activated delayed fluorescence device with a mixed host

Abstract

The temperature dependence of organic light-emitting diodes (OLEDs) with green thermally activated delayed fluorescence (TADF) was investigated in this study. The temperature-dependent driving properties of an OLED device based on TADF were analyzed and its transient electroluminescence characteristics at various temperatures were investigated. TADF materials feature an additional mechanism called reverse intersystem crossing (RISC) that is forbidden in conventional fluorescence. The ratio of RISC is known to be proportional to temperature. We found that the luminance of the device with a TADF material was dependent on the temperature when under fixed voltage but not when under a fixed current density. In addition, the spectrum, luminance, and power efficiency were slightly shifted as the temperature was varied from −20 °C to 50 °C. Moreover, with increasing temperature and the use of a mixed host, the rising- and decay-time properties were improved. Lastly, the dependence of device performance on the host ratio was analyzed. The results revealed that temperature dependence of rising time was due to influence of increase in both mobility and ratio of RISC, while that of decay time was mainly attributed to ratio of RISC.