Associate Professor, College of Chemistry and Molecular Sciences, Wuhan University, China

Biography: Dr. Guohua Xie obtained his Ph.D. degree from Jilin University (China) in 2011, investigating active matrix organic light-emitting diodes (OLEDs) and demonstrating the first prototype of QVGA OLED microdisplay in China. From August 2011, Dr. Xie carried out his postdoctoral research at TU Dresden (Germany), sponsored by Alexander von Humboldt Foundation, investigating the stability of OLEDs. From January 2013 to January 2015, Dr. Xie worked for an interdisciplinary project funded by Engineering and Physical Sciences Research Council (EPSRC, UK) at the Organic Semiconductor Center of the University of St Andrews, quantifying the spatial coherence lengths of OLEDs for the first time. Since January 2015, he is an associate professor at the College of Chemistry and Molecular Sciences of Wuhan University (China). Dr. Xie gained extensive experience in the interdisciplinary research of materials and physics of organic optoelectronics. He has coauthored more than 80 peer-reviewed publications (h-index of 24.)

Speech Title: High-Performance Thermally Activated Delayed Fluorescence Polymers for Light-Emitting Devices
Abstract: Thermally activated delayed fluorescence (TADF) materials are considered as the third generation ones for organic light-emitting devices (OLEDs) after the fluorescent (1st generation) and phosphorescent (2nd generation) materials. To meet the requirements of low-cost and mass-production for practical application, we developed a series of TADF polymers including blue, red and single component white polymers.
For the blue TADF polymers, based on our previously developed D1-A-D2 type TADF small molecule, side-chain engineering was applied. According to the theoretical calculation, the distribution of molecular orbitals of the TADF polymers is almost identical to that of the TADF small molecule used as the side-chain component, i.e., the TADF features of the small molecule were completely inherited by the polymers, which led to a considerably high photoluminescence quantum yield (PLQY) up to 74% in toluene and high reverse intersystem crossing rate of 8.6 × 105 s-1. With a TADF small molecule with PLQY of ~100% as the sensitizer, we improved the PLQY of the polymer-based film up to 95% and thus an external quantum efficiency (EQE) over 15% at a practical luminance of 100 cd/m2 was achieved.
By managing the emission from the backbone and the TADF component of the polymer based the alternating fluorine and dibenzothiophene-S,S-dioxide, we demonstrated a warm white emission TADF polymer based LED with near 10% EQE and a red TADF polymer based LED with a maximum EQE up to 19.4% for saturated red emission by using the backbone-donor/pendant-acceptor strategy.