Synthesis And Research Of New Donor And Acceptor Materials For Organic Solar Cells

This thesis introduces the research status of donor material and acceptor materials for polymer solar cells. In the development of polymer solar cells, acceptor material and donor material both have profound effects on the performance of polymer solar cells. We designed and synthesized D-A conjugated polymers based on benzo[1,2-b:4,5-c’]dithiophene-4,8-dione (BDTD); and we also designed and synthesized a fullerene derivative as an acceptor in PSCs. Specific results are as follows:1. Two D-A copolymers as donor materials were synthesized, including Poly{7-(3-(2-butyloctyl)-5’-methyl-[2,2’-bithiophen]-5-yl)-5-(4-(2-butyloctyl)-5-methylthiophen-2-yl)-2-(2-ethylhexyl)benzo[1,2-b:4,5-c’]dithiophene-4,8-di one}(PThBDTD) and Poly{7-(4-(2-butyloctyl)-5-(5-methylthieno[3,2-b]thiophen-2-yl)thiophen-2-yl )-5-(4-(2-butyloctyl)-5-methylthiophen-2-yl)-2-(2-ethylhexyl)benzo[1,2-b:4,5-c]dithiophene-4,8-dione} (PTTBDTD) with BDTD as the acceptor unit and thiophene (Th) or thieno[3,2-b]thiophene (TT) as the donor unit. They have medium optical bandgaps, corresponding to Eg of 1.72 eV for PThBDTD and 1.61 eV for PTTBDTD, respectively. Both polymers possess broad absorption, good solubilities and good hole mobilities. Finally, with PC71BM ([6,6]-phenyl-C71-butyric acid methyl ester) as the acceptor, PThBDTD:PC71BM and PTTBDTD:PC71BM solar cells gave power conversion efficiencies (PCEs) of 6.32% and 6.00%, respectively;2. Fullerene acceptor Methano-PC71BM (Methano-[6,6]-phenyl-C71-butyric acid methyl ester) possessed a methylene group more than PC71BM, which were synthesized from pure C70. And their open circuit voltages (Voc) were 0.76 V for Methano-PC7iBM and 0.65 V for PC71BM. PC71BM film absorption was stronger than that of Methano-PC71BM in shorter wavelength (350-500nm), so Jsc of the former was 9.15 mA·cm-2, the latter was 8.84 mA·cm-2, respectively. Two fullerene acceptors both have has good solubilities in conventional solvents (chloroform, chlorobenzene, 1,2-dichlorobenzene, etc.) and they also have high electron mobilities. As a result, P3HT:Methano-PC71BM and P3HT:PC71BM solar cells gave PCEs of 4.45% and 3.97%, respectively.