The Synthesis And Characterization Of1,3,5-triazines And Diketopyrrolopyrrole (DPP)-based Materials For Organic Photovoltaic Cells

Organic solar cells (OSCs) have attracted considerable interest due to their potential for large-scale, cost-effective and environmentally friendly power generation. In OSCs, small molecules (SMs) are of increasing interest due to their outstandingly high absorption coefficients and simple purification procedures in contrast to commonly used conjugated donor polymers, such as poly (3-hexylthiophene)(P3HT). However, most of the energy conversion efficiency obtained from the devices which used small molecule materials is in4%the following. Besides these, a small number of new materials and the lack of a systematic study of SMs research based on the bulk heterojunction (BHJ) concept are very obvious. That is to say the research of new small molecule materials for organic photovoltaic cells has very wide development space. So the main target of our research is to synthesize small molecule photovoltaic materials which have favourable solubility, wide absorption spectrum and high charge transfer efficiency.In this article, we choose1,3,5-triazines and Diketopyrrolopyrrole (DPP) as the central structure to synthesize small molecule photovoltaic materials.Diketopyrrolopyrrole (DPP) is a specific structure with two conjugate rings which is composed of the structures of lactams. The small molecules based on DPP have strong interaction because of the p-p functions. So the structure has low HOMO, LUMO and narrow energy band gap. Through the design and synthesis of small molecule materials based on DPP, we can synthesize the SMs which have wide absorption spectrum and high charge transfer efficiency. And by contecting the alkyl chain to the N atom in the structure of lactam, the solubility of the small molecule can be improved obviously. In this article, we have synthesized three small molecule photovoltaic materials based on DPP. And according to the theoretical calculation result, we have tested the HOMO, LUMO and the absorption spectrum of the materials, all of which meet the demand of being OSCs materials. Among the three small molecule materials, the structure of DHFDPP has the best ability of forming the film. So we used this material as the donor and made the solution-processed bulk heterojunction device. Then we tested the photovoltaic performance of the device and the energy conversion efficiency is0.5%, the work of optimizating the device is still in progress.The structure of triazines is a strong electron withdrawing group. The derivatives of the triazines have been widely used in many respects, such as metal complexes, liquid crystal materials and organic photoelectronic materials. But few articles have reported the OSCs materials based on triazines. So we use the2,4,6-tris(4-formyl radical)benyl-1,3,5-triazines and the nitrophenyl acetonitrile as the raw materials to synthesize the small molecule OSCs materials. In the progress of synthesizing the2,4,6-tris(4-formyl radical)benyl-1,3,5-triazines, we found that the derives of1,3,5-triazines can be synthesized thourgh the Ni catalyst reactions under mild conditions. So we have optimizated the synthesis method and synthesized a series of derives based on1,3,5-triazines.