The Synthesis Of Low Band-gap Organic Photovoltaic Materials And Its Application

Solar energy is a renewable, cleanly, and inexhaustible energy, and fabricating solar cells can be a directly and effective method to utilize the solar energy. Polymer solar cells have attracted significant attentions due to their easy fabrication, low cost, light weight, large-area, flexibility on device and the polymer can be easily modified. In this thesis, systemmatic introduction was used to present the research of polymer solar cells. So far, some achievements was obtained, and the power conversion efficiency (PCE) of the cells were beyond8%, but some serious problem should be resolved, such as the mismatch of the absorption of polymer solar cells and the solar emission spectra, the short life of cells. We retrieve the polymer materials which absorption of solar spectra can be red-shift and broaden absorption. Solar cells were fabricated after blending with the PCBM acceptor as the active layer, and the corresponding power conversion efficiency were tested.1. Malonate used as strong withdrawing electron group was introduced into the side chain of the thiophene, and the dialkyl2-(thiophen-3-ylmethylene)malonate (DTM) were designed as the acceptor unit to cross-couppled with the donor to get the conjugated polymers with the donor-acceptor structure. The target polymers exhist thermal stability, deep-lying (high occupied molecular orbit (HOMO) energy level, and they were used as the donor blending with the [6,6]-phenyI-C-71-butyric acid methyl ester (PC71BM) to form the active layer of polymer cells, and among the series of polymers,the best performance of devices was P2, and its PCE was1.22%, with Voc of0.70V, Jscof4.5mA/cm2and FF of38.8%.2. Strong electron withdrawing acceptor unit,4,7-bis(5-bromothiophen-2-yl)-5,6-bis(octyloxy)(BBTBOBSDZ), was designed and synthesized. And it cross-coupled with the4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b’]dithiophene (BEHTBDT) with the core, BDT, as the donor unit to obtain the alternative conjugated polymer P2, and the thermal properties, electro-chemical properties, and the polymer showed broad absorption spectra, which may match the solar emission spectra, resulting in better collection of solar energy. The bulk-hetero junction solar cells constituted with polymer used as the donor blending with the PC61BM as the acceptor were fabricated, and their photovoltaic properties were tested and the best performance of the devices was0.81%, blending with PC71BM as the active layer of the polymer solar cells.