Development and Optoelectronic Applications of Spirobifluorene-Based Materials and Solution-Processable OLEDs Materials
Date Issued
2010
Date
2010
Author(s)
Lin, Chi-Yen
Abstract
1. Spirobifluorene-Based Materials for Optoelectronic Applications
Recently, molecules possessing a 9,9''-spirobifluorene core are used widely in organic optoelectronics. In this dissertation, different functional groups were introduced to form 2,2''-A,7,7''-B-substituted spirobifluorene (left-right asymmetric). The bridging of two chromophores perpendicularly via a sp3-hybridized atom into a spiro configuration hinders the aggregation between molecules. In addition, optically active enantiomer is possible to obtain in the left-right asymmetric system. First, (S)-BrSOH and (R)-BrSOH were resolved by clathrate formation between racemic dissymmetric 2,2''-dihydroxy-7,7''-dibromo-9,9''-spirobifluorene and the resolving reagent. New enantiomerically pure spiro compounds bearing pyrene moieties were synthesized and capable of preferentially absorbing and emitting circularly polarized light (glum ~ 0.001). Second, a new dye (SSD1) featuring two donor/acceptor chromophores aligned in a spiro configuration with two anchoring groups separated at a distance of 10.05 A (closely matching the distance between the adsorption sites of the anatase TiO2 surface) undergoes efficient dye adherence on TiO2 films. A dye-sensitized solar cell incorporating SSD1 exhibited a power conversion efficiency of 3.75%. Third, spirobifluorene-based donor (triphenylamine)–acceptor (cyano) bipolar systems has been investigated. Organic films (CN1) were formed on gold electrode by electrochemical polymerization. The gold surface work function can be changed over more than 0.4 eV depending on the numbers of electrochemical deposition cycles.
2. Development of All Solution-Processed Multilayer Organic Light-Emitting Diodes (OLEDs)
Compared to vacuum deposition technique, solution-based deposition is more attractive for next generation OLEDs because of the simple process and low instrumental cost. The overall theme of this dissertation is to overcome the difficulty in achieving purely all-solution processing multiple-layer OLEDs and understanding the resulting complex interfaces. In order to alleviate the interfacial mixing problem, two promising approaches are investigated here. The first approach is the use of an organic-soluble precursor that becomes insoluble through crosslinkable reactions. With such a concept, thermally crosslinkable hole injection materials (HIMs) and/or hole transport materials (HTMs), emitting materials (EMs), and electron transport materials (ETMs) were designed and synthesized. These crosslinked HTMs, studied using time-of-flight techniques, exhibited remarkable stability and non-dispersive hole transport properties, with values of
Subjects
Spirobifluorene
Optoelectronic Applications
Solution-Process
Organic Light-Emitting Diodes
Polymerizable Reactions
Type
thesis
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