Study on Stability of Thermally Activated Delayed Fluorescent OLED

The Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes (TADF-OLEDs) was fabricated, using bipolarmaterial 4, 4'-bis (carbazol-9-y1) biphenyl (CBP) as host, green fluorescent material (4 s, 6 s)-2, 4, 5, 6-tetra (9 H-carbazol-9-yl) isophthalonitrile (4CzIPN) as dopant. The device structure was optimized by adjusting concentration of 4CzIPN doped into CBP, then the photoelectric properties and lifetimes of device were studied. The performance of 12% 4CzIPN-doped device is the best. To study the influence of driving mode on device lifetime of the TADF-OLEDs, the AC driving circuit of positive constant current reverse constant voltage was designed, and the parameters of the AC driving circuit were optimized and adjusted. Research shows that the TADF-OLED achieved a longer device lifetime under AC driven of frequency of 50 Hz, reverse bias of 0 mV and duty cycle of 50%. By comparing the lifetime curves of the same device driven by DC and AC, it is found that the TADF-OLED lifetime under the AC driving scheme is about 1.5 times longer than that of under the DC driving scheme.