| Summary: | 碩士 === 國立臺灣海洋大學 === 光電科學研究所 === 104 === In first part of the thesis, we report bipolar host molecules composed of carbazole, triarylamine, and bipyridine were synthesized and applied in multi-color PhOLEDs. PhOLEDs were fabricated using green [(ppy)2Ir(acac)], yellow [(bt)2Ir(acac)], and red [(mpq)2Ir(acac)] as doped emitters, which showed low driving voltage, high external quantum efficiency (EQE), and extremely small efficiency roll-off. Moreover, the device containing 2Cz-44Bpy: 10% (ppy)2Ir(acac) showed an unprecedentedly high EQE of 22% (79.8 cd A−1) and PE of 102.5 lm W−1 at a practical brightness of 100 cd m−2. In addition, the extremely low roll-off efficiency and driving voltage are 21.6% EQE and 2.8 V at a practical brightness of 1000 cd m−2.
In second part, we report bipolar TADF-host molecules based on carbazole and cyano under different position. TADF-OLEDs were fabricated using green [4CzIPN], yellow [4CzTPN], and red [4CzTPN-Ph] as doped emitters, which showed low driving voltage, high EQE, and small efficiency roll-off. Moreover, the device containing ms83: 10% 4CzIPN showed an unprecedentedly high EQE of 22.7% (68.8cd A−1) and PE of 69 lm W−1. At a practical brightness of 1000 cd m−2, the device still can maintain EQE of 19.3%.
In third part, we report both t-HTTH and t-MTTH undergo a reversible type excited-state intramolecular proton transfer (ESIPT). The pre-equilibrium in the excited state leads to both normal (~440 nm) and proton-transfer tautomer (~560 nm) emissions, for which the intensity ratio is dependent on both the molecular structure and the polarity of surrounding media. As a result, the emission can be widely tuned from blue to yellow via white-light luminescence. Based on t-MTTH, a white organic light emitting diode (WOLED) was successfully fabricated, achieving EQE of 1.70% with CIE coordinates of (0.29, 0.33). More importantly, the electroluminescent spectra show superior color stability that is independent of luminance. The result demonstrates for the first time a credible WOLED based on a unimolecular ESIPT reaction, which may have far-reaching implications for practical application.
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