Synthesis, Properties, and Applications of Carbazole and Fluorene Based Donor-Acceptor Materials
Date Issued
2010
Date
2010
Author(s)
Chi, Liang-Chen
Abstract
This thesis is composed of two major parts. For the first part, we have successfully synthesized a series of bipolar hosts by introducing two electron-withdrawing moieties onto the 3 and 6 positions of N-phenyl carbazole. The introduced electron-withdrawing blocks are dimesityl boron, phenylbenzimidazole, pyridine, and oxadiazole. The new molecules obtained by different structure combinations have led to different film-forming property, comparable electron and hole mobilities, tunable triplet energies and energy levels which govern their various applications as host materials in phosphorescent organic light-emitting devices (PhOLEDs) with good to excellent external quantum efficiencies (EQE). Among those, CMesB can serve as host material for doping with Firpic (ηext = 12 %, ηp = 19 lm/W) and Ir(ppy)2acac (ηext = 16 %, ηp = 34 lm/W) to realize efficient blue and green PhOLEDs, respectively. High performance PhOLEDs have been achieved with COxaPh as host material doping with green emmitters Ir(ppy)2acac (ηext = 18 %, ηp = 76 lm/W) and red emmiter OS2 (ηext = 21 %, ηp = 36 lm/W). CBzIm can dope with NFirpic) to get a blue PhOLED with EQE up to 16 % and ηp = 29 lm/W. Due to its high photoluminescence, CPhBzIm was not only used to fabricate non-doped deep blue-emitting devices with promising performance (ηext = 3 %, CIE = 0.16; 0.05), but also served as host material doped with Ir(pbi)2acac to realize green PhOLED (ηext = 19.2 %, CIE = 0.42; 0.56). Furthermore, we have demonstrated a simple single-doped way to realize two-color based WOLEDs (ηext = 7 %, CIE = 0.31, 0.33) by using the dual roles of CPhBzIm. CNBzIm served as a universal host host material for Firpic (13 %, ηp = 31 lm/W), Ir(ppy)2acac (18 %, ηp = 59 lm/W), OS2 (ηext = 19 %, ηp = 27 lm/W), and WOLEDs (ηext = 16 %, ηp = 37 lm/W). CAymPy and CSymPy have similar physical properties which were applied as host materials gave devices with Ir(ppy)2acac as emitter (CAymPy, ηext = 12 %, ηp = 47 lm/W, CSymPy, ηext = 11 %, ηp = 42 lm/W) and Ir(mpq)2acac as emitter (CAymPy, ηext = 11 %, ηp = 12 lm/W；CSymPy, ηext = 8 %, ηp = 9 lm/W).
The second part, we have successfully synthesized a series of novel bipolar molecules with various donors and acceptors which were bridged with a fluorene conjugation. The donors, mainly diaryl amino groups, were introduced onto the C3 and C6 of the fluorenone core employing Hartwig’s palladium-catalyzed C-N bond coupling reaction of 3,6-dibromofluorenone and diarylamines. After then, cyanoacetic acid, dicyano , and diethyl malonate were introduced as the acceptor parts onto the 9-position of the fluorenone by Knoevenagel condensation. Those bipolar materials have shown to have potential applications of organic thin-film solar cell and photodynamic therapy. The photovoltaic bulk heterojunction solar cells with p-type LCC-1 as the dye in combining with C60 as the electron acceptor have been fabricated by thermal evaporation. These devices have reached power conversion efficiencies of ~1 % and IPCE at 498 nm up to 35 % under simulated AM 1.5 solar irradiation at 100 mWcm-2. In addition, compounds 17 was found to exhibit larger two-photon absorption (TPA) cross section value of 1636 GM as measured by the two photon induced fluorescence. More strikingly, the best single-photon singlet oxygen generation quantum yield (>100 %) as compared to that of the standard tetraphenylporphyrin (H2TPP) was observed, which indicates the highly potential application in photodynamic therapy is possible in the dye can be designed to interact with cells.
Subjects
Carbazole
Fluorene
organic light emitting diode
organic solar cell
two photon absorption
SDGs
Type
thesis
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