Synthesis And Study Of Organic Photovoltaic Materials Containing Benzodithiophene And Rhodanine

As the stocks of fossil fuel are diminishing dramatically, many researchers pay a lot of attention to the renewable, clean energy sources, such as geothermal energy, wind energy, solar energy. Among them, solar energy is one of the most promising solutions for energy depletion. Currently, solar cells based on inorganic silicon have achieved commercial application. However, the expensive silicon purification technology and environmental pollution is the main barrier that prevents silicon-based solar cells from providing a large fraction of energy. Among them, organic solar cells are a promisingly photovoltaic technology with the advantages of low-cost, flexibility, and light-weight. However their low power conversion efficiencies have restricted their use in commercial application, needing many researchers to exploit new kinds of organic photovoltaic materials. Hence, the article designed and synthesized two kinds of organic small-molecules and conjugated copolymers for organic solar cells. We have carefully investigated their UV-Vis absorption, thermal, electrochemical and photovoltaic properties.1. Two A–D–A type organic small molecules: the small molecule S1-DTBT with 3,4-dimethoxythiophene as the core and the DTBT unit; the small molecule S2-7TRD with seven-thiophene as the backbone and rhodanine as the end electron-withdrawing group. We have concretely investigated the effects of the units DTBT and rhodanine on their properties. The two molecules demonstrated good thermal performance. The introduction of DTBT successfully decreases its HOMO energy level and improves its solubility. And rhodanine can improve the UV-Vis absorption intensity of S2-7TRD. Therefore, short-circuit current of S2-7TRD is neary double that of S1-DTBT.2. Four conjugated copolymers(PBDT-TRD, PBDT-3TRD, PBDT-TTRD, and PBDT-3TTRD) based on 3-ethylrhodanine in the side chains have been designed and synthesized. It is the first time to introduce a rhodanine unit into the side group of the conjugated polymers. We have carefully studied the effects of the conjugated π-bridge and 3-ethylrhodanine unit on their properties. These copolymers demonstrated good thermal performance, broad absorption spectra, and deep HOMO energy level. The polymer solar cells have been fabricated by using these copolymers as donors and PC61 BM as the acceptor. Among them, the devices based on PBDT-TRD and PBDT-TTRD demonstrated preferable power conversion efficiencies of 3.35% and 3.18%, respectively, and PBDT-TRD have gained the highest open-circuit voltage of 0.94 V.