Abstract
Abstract In the past several decades, conjugated polymers have been extensively and intensively investigated because of their unique electroluminescent properties. The most well known application of these materials is the organic light emitting diodes. It is not only used in display technology, but also applied in lighting, such as backlight module of TFT-LCD, general light source, and organic solar cells. In this thesis, we investigated the gas route preparation and optoelectronic properties of PPV, inorganic/organic hybrid system, and pyrolytic carbon. The relationship between the structure and optoelectronic properties has been investigated. The three main topics of this research are: 1) Conjugated polymer thin film preparation with CVDP (chemical vapor phase deposition polymerization) methods︰The SPR method was employed to synthesize PXT to be a precursor of a liquid phase route. Both FTIR and NMR spectra were obtained to identify the composition of the intermediate and final product in the reaction. The precursor, PXT, was cast on the substrate via spin coating, and formed PPV films after thermal convertion. Besides, we used a CVDP method to prepare PPV films and compared the PL quantum yields with those from the PPV films prepared by spin coating. The results showed that the PPV films prepared by the CVD method exhibited lower PL quantum yields. It may be caused by the dense structure of the CVD films, leading to concentration quench of the luminescent centers. We also used the same method to prepare poly(p-phenylene) films in one-step successfully. The polymer chain conformation of the film can be effectively adjusted through a simple surface treatment of the substrate. The variations in film morphology induced by the substrate characteristics led to significant changes in the optoelectronic properties of the film. 2) Organic/ Inorganic hybrid system preparation with CVDP method: The highly photoluminescent Zn/PPV complex films were successfully prepared with a direct complexing of Zn to PPV in a facile CVDP process for the first time. A two order of magnitude improvement in PL quantum yield was achieved through this metal complexing. The present approach can be readily extended to other photoluminescent metal-polymer systems. Besides, a novel co-fed chemical vapor deposition polymerization process was developed to successfully fabricate PPV-CdS and PPV-ZnS nanohybrids. The morphology of the nanohybrids can be effectively tuned through a simple control of the relative precursor concentration in the deposition system. Markedly different nanohybrid morphologies, ranging from well dispersed nanocrystals to continuous bulk heterostructures, were realized. The variations in morphology corresponded to according variations in optoelectronic properties attributable to the the p-n interfaces formation. 3) A pyrolytic carbon thin layer deposited on quartz substrate serving as a counter electrode for dye-sensitized solar cells: The chemical vapor deposition (CVD) pyrolytic carbon thin layer deposited on quartz substrates from biphenyl ring precursor monomer 4,4'-bis-chloromethyl-1,1'-biphenyl and served as a CE for DSSC applications was investigated. The material possesses metal-like, hydrophilic, microporous, conductive, and catalytic properties. We demonstrated that the catalytic properties with the CV and EIS methods. Although the catalytic activity was less than that of the traditional Pt counter electrode, the pyrolytic carbon material has a room for improvement and may potentially replace the noble metal electrode in DSSC applications. From the present study, the conjugated polymer’s chain conformation, film morphology, dimension, and dopant were found to affect the luminescence position, strength, and efficiency. As for the new carbon material for the DSSC applications, the catalytic activities dominate the conversion efficiency.