A step-by-step strategy to enhancing the photovoltaic performance of indandione-based polymers

A series of conjugated polymers, poly(2-(5-hexylthiophen-2-yl) methylene-1H-indene-1,3(2H)-dione benzodi-thiophene) (IND-HT-BDT) and poly(2-(5-hexylthiophen-2-yl) methylene-1H-indene-1,3(2H)-dione fluorinated benzodithiophene) (IND-HT-BDTF), based on 1,3-indandione derivatives are designed and synthesized for organic solar cells (OSCs). The polymers have a typical architecture of donor - acceptor (D-A) configurations with 2-(5-hexylthiophen-2-yl) methylene-1H-indene-1,3(2H)-dione (IND-HT) as the electron acceptor and the benzodithiophene (BDT) or fluorine substituted benzodithiophene (BDTF) as the electron donor. To investigate the photovoltaic properties of the polymers as the polymer donor, inverted OSCs are fabricated based on the polymer as the donor and fullerene acceptor (6,6)-Phenyl C71 butyric acid methyl ester (PC71BM) or 2,2'-((2Z,2'Z)-((12,13-bis(2-butyloctyl)-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno [2",3":4',5']thieno[2',3': 4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis (methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)) dimalononitrile (Y6BO). IND-HT-BDT and IND-HT-BDTF based devices as the polymer donors and Y6BO exhibit the power conversion efficiency (PCE) of 4.82% and 6.43%, respectively, which are better than the corresponding devices based on PC71BM as the acceptor. This is due to the comple-mentary absorption ranges between donor polymers and those Y6BO acceptors.