| Summary: | 碩士 === 國立臺灣海洋大學 === 光電科學研究所 === 100 === In this thesis, we study a series of bipolar universal host to apply in PhOLEDs. The morphological, thermal, photophysical properties and carrier mobility of these host materials are affected the device performance.
In the first part, two new bipolar host molecules by adoption of interrupted -conjugation at C9 carbon of fluorene unit between the electron donating carbazole and electron withdrawing CN/oxadiazole group at C3 position of fluorene moiety. CzFCN and CzFOxa exhibit high triplet energy (ET = 2.86 – 2.70 eV), morphological stabilities and bipolar character with balanced charge mobilities (10‒5 ~ 10‒6 cm2 V‒1s‒1). By employing these materials as host and doped with various color phosphors, we have successfully fabricated highly efficient PhOLEDs from blue to red (15.1%- 20%). Then, we design single-host WOLEDs within R-G-B colors. The white device can realize outstanding efficiency (17.3%, 33.7 cd A‒1, 30 lm W ‒1), CRI (89.7) and color stability trade-off (CIEx = 0.44 – 0.45 and CIEy = 0.43 at applied voltage of 7 to 11 V). In the second part, we developed CzFCN’s derivatives as universal bipolar host(CzFCN2 and CzDFCN), which showed lower efficiencies than that used CzFCN as host.
In the third part, a systematical comparison of physical properties and their dual-role (host and electron transport) applications of star-shaped 1,3,5-triazine-based ET-type hosts (T2T, 3N-T2T, and 3P-T2T) with differential peripheral groups was reported. The introduction of N-heterocyclic polar peripheries onto 1,3,5-triazine core gave evident benefit to the electron injection/transport properties, rendering efficient PhOLEDs with simpler device configuration feasible. Among these hosts, 3P-T2T can serve both as promising host and electron-transport material for various phosphors (from blue to red), which exhibited low operation voltages with maximum EQE of 8%, 15.7%, 16.9%, 16.4% and 10.8% for sky blue, green, yellow, red and white, respectively.
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