| Summary: | 碩士 === 國立交通大學 === 應用化學研究所 === 98 === Seven tri-arylamine-based hole-transporting materials (HTMs) bearing thermally cross-linkable vinyl groups have been synthesized and characterized. These HTMs could be in situ cross-linked under mild thermal polymerization without any initiator. After cross-linking, the resultant HTMs form robust, smooth, and solvent-resistant networks, which enables the subsequent spin-coating of emissive layer (EML). The HOMO energy levels of the HTMs can be fine-tuned by introducing electron-withdrawing groups or electron-donating groups on the phenyl ring para to the nitrogen. The polymer LED devices with configuration of (ITO/HTLs/PFO/CsF/Al) were fabricated and characterized. The device luminous efficiency is improved because the HTLs can facilitate cascade hole injection and transport, and function as an efficient electron blocker. Most importantly, the milder cross-linking condition for these HTMs allows the commonly used conducting polymer, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), to be incorporated as the bottom hole-injecting layer to reduce the turn-on voltage and improve the luminous efficiency of the devices. In the electroluminescence spectra, in addition to the blue emission from the polyfluorene, we found that these devices showed an emission band at the longer wavelengths, which is proved to be the exciplex emission between the fluorenone spcies and HTMs. On the other hand, the devices with the configuration of (ITO/HTLs/S2Y/TPBI/LiF/Al) using PPV-type yellow emitting polymer SY2 were also fabricated and evaluated. However, due to the electron-dominating properties of SY2, we found that introduction of the HTLs will slow down the hole transport in the devices, thus resulting in unbalanced charge carriers and reduced luminous efficiency. However, the brightness of the devices is generally improved. We envision that the strategy of using styrene as an efficient cross-linker can also be integrated with various HTMs with different properties for realizing high power efficiency white PLED in the future.
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