Design, Synthesis And Properties Of Conjugated Copolymers/Molecules Based On Building Blocks With Lactam Group

Organic solar cells (OSCs) have attracted global attention due to their unique advantages of light-weight, flexibility and allowing solution process in a large-area scale. Nowadays, a number of novel conjugated polymers and molecules have been reported and thus OSCs have achieved power conversion efficiency (PCE) over 10%, which has met the demand for their commercialization. Nevertheless, when compared with inorganic semiconductor, organic semiconductors need to conquer obstacles regarding their relatively low charge mobility, which has been proven potential based on those previous discoveries. In the past decade, people have discovered that its charge mobility can be significantly enhanced by introducing lactam containing moieties into the conjugated back bone. This enhancement is ascribed to the stronger interchain π-π stacking.In chapter 2, a lactam containing monomer 5-alkylphenanthridin-6(5H)-one(PN) and its regioisomer 6-alkyloxyphenanthridine(PO) were synthesized, and subsequently, as donor units, were copolymerized with DBT to obtain two medium bandgap polymers with deep HOMO levels, which accounted for the high open circuit voltage for both resulting devices. What’s more, the polymer PDBTPO is of the highest efficiency with blended with PC71BM, achieving a PCE of 3.77%. To get deeper understanding of these polymers, extra characterizations, such as absorption and morphology, are also carried out in order to find out the origin of their varied performances.On the base of chapter 2, here in chapter 3, lactam containing moieties, 5-alkylphenanthridin-6(5H)-one(PN) and 4-alkyldithieno3,2-b:2’,3’-dpyridin-5(4H)-one (TN), were introduced to build to large bandgap electron acceptors. Considering the weak electron withdrawing ability of PN and TN, the LUMO level of the resultant acceptors were low enough to facilitate electron transport when a relatively weak acceptor rhodanine is linked. These two large bandgap electron acceptors are surely potential in organic solar cells for the matching of absorption spectrum with most electron donors of high efficiency nowadays.In the fourth chapter, two regioregular conjugated polymers and their regiorandom counterparts are synthesized via C-H activation polymerization. Plus the effect of Pd catalyst amount on the molecular weight was also studied. Detailed comparisons of these two groups of polymers were examined by their absorption profiles and electrochemical measurements, and their differences are successfully explained by the results of DFT calculations.