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A pair of isomeric hexafluorinated oligomers (Th6FSe and Se6FTh), which are with the same aromatic compositions (difluorobenzothiadiazoles central core, IDT units, and donor end-capped groups), but differ in the π-bridge position (selenophene and thiophene), were designed and successfully synthesized. The potential of the resulted oligomers as donor materials for BHJ-OSCs was systematically investigated through optical absorption, AFM, TEM, GIXD, charge mobility measurement, and photovoltaic device fabrication. It was found that the π-bridge sequences in the resulted oligomers play a subtle but key role in device performances. Moreover, as a result of increase of crystalline content and desired phase separation after rapid SVA or combined TA and SVA treatment, the device performance of the resultant devices undergo significant enhancement. Notably, the Se6FTh devices showed a best PCE of ca. 9.3% with SVA+TA treatment, which is the highest PCE of BHJ-OSCs based on donor end-capped oligomers. These primary...

A family of narrow band gap extended π-conjugated D2-A2-D1-A1-D1-A2-D2 type small molecules based on diketopyrrolopyrrole derivatives as the stronger acceptor core (A1) coupled with indacenodithiophene (IDT; D1) and difluorobenzothiadiazole (A2) are synthesized, and their properties as donor materials in solution-processed small-molecule organic solar cells are investigated. The impacts of replacing the thiophene ring by a more electron-deficient thiazole ring and inserting thiophene spacer between electron-donating (D1) and electron-accepting (A1 and A2) aromatic moieties on bulk properties, such as the photophysical properties, the HOMO/LUMO energy level, charge carrier mobilities, and the morphologies of blend films, as well as optimization on device performance via solvent vapor annealing are investigated. NDPPFBT shows outstanding efficiencies up to 7.00% after THF vapor annealing for 60 s because of a very high fill factor (FF) of 0.73 and high Voc of 0.89 V. The reported efficiency is among one of ...