The Research Of Photo-induce Charge Transfer Between C60and PVK In Their Surface And Interface

Fullerene family has been widely used with the development of photo-induced chargetransfer properties for development of new optical materials, for its special cage-like structure,highly symmetric electron excellent ability and stability since its discovery. Compared to manyelectron donors, C60can be used as a photosensitive electron acceptor. For organic optoelectronicmaterials, because of its unique features such as flexible, inexpensive, it has important scientificsignificance and value of research in the filed of a flexible device. Wherein PVK(poly-vinylcarbazole) is a well-known hole-conducting material, when mixed with C60, it is usedas electron donor. The charge transfer studies on p-n heterojunction structure were very importantfor such donor-acceptor complex film. High photocharges transfer efficiency is also a primaryfactor for the use of solar energy. In this paper, samples were prepared by spin-coating andspin-coating combining with thermal evaporation to form different contact interface, such asbuk-heterjunction and donor-acceptor bilayer structure. Scanning Probe microscopy (SPM),UV-Vis absorption spectroscopy and the photoluminescence (PL), surface photovoltagespectroscopy (SPS) and I-V measurement were used to characterize these samples. It confirmedthat there were both good photoelectric behaviors for these two kinds of structures. This papercovers the following three aspects:1. The film forming condition research of polymer PVK and PVK combining with C60by spin-coatingWe study the film forming conditions of PVK, which has good film-forming in different spinspeeds with low and high concentration. Then we used the best parameter to explore the bettercondition of PVK combining with C60. Next we studied the impact of others factors for compositefilms. SPM images showed that the morphology changes. UV-Vis absorption spectroscopy wasused to qualitatively prove that C60kept in the composite films through spin-coating.2. The research of photo-induced charge transfer between PVK and C60by spin-coatingThe PL of composite PVK/C60with different molar ratios was compared with PVK film. Theresults show that there was a large decrease in intensity of fluorescence when the molar ratio of PVK and C60is2:1. Then we choose this sample to test its photoconductivity through SPS and I-Vtest. Photovoltage signal appears between320nm~540nm. I-V measurement results show thatthe current can improve nearly3orders of magnitude when sample was exposed to ultravioletlight. For the double layer structure of PVK/C60by spin coating, morphology, absorptionspectroscopy, PL, surface photovoltage and C-AFM test were investigated. The morphology andabsorption spectrum prove that C60can be prepared successfully by spin coating method on PVKfilm. It also appeared PL quenching phenomenon, and had photovoltage signal. C-AFM resultsproved the phenomenon of photo-induced charge transfer between PVK and C60for this doublestructure.3. The research of photoinduced charge transfer between interfacial contact PVK andC60The PVK/C60donor-acceptor double structure was formed by the way of combining spincoating and thermal evaporation. SPM, UV-Vis absorption spectroscopy, PL, SPS and I-Vmeasurement were also used to characterize this double structure. The sample of PVK spinned onC60films shows fluorescence intensity decreasing and photovoltage signal appeared. I-V curvesshowed the current can improve nearly3orders of magnitude when it was exposed in ultravioletlight, which is similar for the buk-heterjunction structure.