Syntheses, Properties and Applications of Organic Optoelectronic Materials
Date Issued
2007
Date
2007
Author(s)
Fang, Fu-Chuan
DOI
en-US
Abstract
Abstract
Chapter 1 : Three series of novel 4,5-diaza-9-9’-spirobifluorene (SB)-incorporated organic materials have been synthesized and characterized. For the SB-incorporated terfluorene materials, we used the molecular doping strategy to introduce 4,5-diaza-9-9’-spirobifluorene (SB) as a functional substituent spirally linked to the conjugated oligofluorene backbone. TSBT exhibits lower device turn-on voltage and higher EQE than that of using T3. Because the conjugated backbone implant with thiophene rings increase the π-conjugation, the spectra of TTSBTT show substantial red shift compared to that of TSBT. Due to the high electron affinity of 4,5-diaza-9,9’-spirobifluorene moiety, SBT, SBB and SB2 were used as the ETL and host materials to simplify the electroluminescence devices. The high EQE (~10.3%) of SBT-simplified device is close to the limit of the emission quantum yield of Btp2Ir(acac) dopant. For the spiro-bridged D-A compound Cz2SB and TPA2SB, the perpendicular arrangement of the donor and acceptor limits the degree of the donor-acceptor interaction in the ground state and allows efficient PET to occur in the excited state. The experimental results show that the efficiency of this PET process was modulated by altering the electronic characteristic of the donor groups.
Chapter 2 : We have reported the syntheses and characterization of two novel cationic iridium complexes, [Ir(ppy)2(SB)]+(PF6─) (orange-red emission) and [Ir(dFppy)2(SB)]+(PF6─) (green emission), for solid-state light-emitting electrochemical cells. The devices using single-layered neat films of [Ir(ppy)2(SB)]+(PF6─) and [Ir(dFppy)2(SB)]+(PF6─) achieve high peak external quantum efficiencies and power efficiencies of (7.1%, 22.6 lm/W) and (7.1%, 26.2 lm/W), respectively. The high efficiencies indicate that the cationic transition metal complexes containing ligands with good steric hindrance (SB) are excellent candidates for highly efficient LECs. Moreover, when we use [Ir(dFppy)2(SB)]+(PF6─) as the host and [Ir(ppy)2(SB)]+(PF6─) as the guest, the host-guest LECs show much enhanced quantum efficiencies (power efficiencies) of up to 10.4% (36.8 lm/W), representing a 1.5X enhancement compared to those of pure host and guest devices.
Chapter 3 : The host materials with high energy gap (T1Si, SP3Cz2, TPA1Si, TPA2Si, CzSi and TRZSi) were synthesized and demonstrated with remarkable properties in the electrophosphorescence. The triplet energies of these host materials were above 2.61 eV in the neat film. In other words, these host materials possessing large triplet energies are suitable for green and blue phosphorescent OLEDs. Moreover, these host materials possess high decomposition temperature above 370 °C and also have high glass transition temperature above 105 °C. The multiple layer devices fabricated with these host materials show highly external quantum efficiency.
Chapter 4 : We developed a straightforward synthesis for introducing self-assembly units into the π-conjugated materials by Suzuki coupling reaction. The novel reagent, 4-pinacolatoboronic ester-benzenebiuret, is an unprecedented building block combining the biuret moiety for recognition function and boronic ester for Suzuki coupling. From the fluorescence confocal microscopy images, the unique morphologies were observed in the mixture of T2-Ph-biuret and OPV-Ph-biuret system with different concentrations. From the scanning electron microscopic (SEM) images, we discovered that T2-Ph-biuret formed globular nanostructure, OPV-Ph-biuret formed fiber nanostructure, and the mixture of 10% doping OPV-Ph-biuret within T2-Ph-biuret gave an irregular morphology on the glass substrates. We ascribed the specific morphology was formed by hydrogen-bonding and/or π-π interactions between OPV-Ph-biuret and T2-Ph-biuret on the substrate surface. Moreover, we observed some special nanostructures on different substrates (ITO and silicon wafer). The change in different shapes could be due to the fact that the surface energies of the substrates are different. In other words, the wetting behavior is different.
Subjects
三聚芴發光材料
分子自組裝
4,5-diaza-9-9’-spirobifluorene
light-emitting electrochemical cells
host materials with high energy gap
self-assembly units
Type
thesis
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