Main research topics of the display device technology laboratory focus on the display and lighting technologies, especially on organic light-emitting diode (OLED), which includes its design, fabrication, and measurements. By investigating the optical, electrical, and material characteristics, a high-quality display and lighting device can be obtained. One of the important goals for this Lab. is to study high-efficiency and long lifetime OLED. We have studied the lifetime elongation of blue triplet-triplet fusion (TTF) OLED, which is the bottleneck for OLED mass production, supported by industry fundings. Several key design rules have been demonstrated and patents were granted. To achieve the high-efficiency and long-lifetime, new molecules and device structures should be optimized. Our Lab. work closely with chemists for obtaining novel materials and used for device design. In device design, one needs to control the electrons and holes to recombine in suitable positions with a suitable way to achieve high efficiency and long lifetime simultaneously. Then, charge carriers recombine to form excitons, which involve different emission mechanisms, such as TTF, thermally activated delayed fluorescence (TADF), and fluorescence, and phosphorescence. Exciton dynamics were widely investigated in this Lab., including triplet exciton energy transfer among different molecules, TTF process, singlet fission process, singlet and triplet exciton diffusion, and exciton quenching process. Excitons radiatively relax energy as photons. We studied the wave propagation in planar and corrugated thin films to extract the photons from waveguiding mode, plasmonic mode, and substrate mode out of the OLED.
