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Two simple dithienosilole unit (DTS)-based nonfused small molecular acceptors (SiOC2C6–4F and SiOC2C6–4Cl) using two DTS moieties linked alkoxyl substituted benzene ring as the central core (D) and bis(5,6-difluro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)dimalononitrile or bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)dimalononitrile as the end groups have been synthesized. The optical, electrochemical properties and device photovoltaic performance of these two molecules were investigated in detail. DFT results indicates S⋯O interactions involving alkoxyl groups of benzyl rings and thienyl S atoms of DTS can act as conformational "locks" to enhance molecular planarity. when the polymer PBDB-T was chosen as the donor, the PBDB-T: SiOC2C6–4F -based device provided a high PCE of 9.68% with a V oc of 0.90 V, a J sc of 17.02 mA/cm2 and an FF of 63.00%, while the PBDB-T: SiOC2C6–4Cl -based device exhibited a PCE of 11.29% with a V oc of 0.87V, a J sc of 20.35 mA/cm2 and an FF of 63.73%, which is so far the best performance reported for organic photovoltaic using silole-based small-molecule acceptors. Simple Dithienosilole unit based nonfused small molecular acceptors based solar cells exhibited a PCE of 11.29%. Image 1 • Two dithienosilole unit-based nonfused small molecular acceptors were synthesized. • S⋯O interactions can serve as conformational "locks" to enhance π-system coplanarity. • SiOC2C6–4Cl exhibit stronger and broader absorption than that of SiOC2C6–4F. • Organic solar cells based on PBDB-T: SiOC2C6–4Cl provide a PCE of 11.29%. [ABSTRACT FROM AUTHOR]

Abstract Side-chain engineering could tune the crystallinity, solubility and aggregation styles of fused-ring electron acceptors (FREAs), and thus could influence the morphology and charge carrier mobility of blend films as well as the final device performances. Herein, we developed a novel FREA called spiro -IDT- O -IC , which is composed of a spiro-bridged IDT core and two 1,1-dicyanomethylene-3-indanone (IC) terminal units. Similar acceptor molecule IDT- O -IC with four 4-octyloxyphenyl side chains is also prepared for the control experiment. The absorptions, energy levels, molecular configurations, and electronic wave functions of these two acceptor molecules have been comparatively studied. Polymer solar cells (PSCs) fabricated with PBDB-T: spiro -IDT- O -IC as the active layer demonstrated a PCE of 6.23% with a J sc of 11.76 mA/cm2, a V oc of 0.84 V and an FF of 0.63. To the best of our knowledge, this is the first report that a spiro-bridged ladder type core was used for the fabrication of fused ring acceptors. Graphical abstract Image 1 Highlights • Lateral fluorene introduced into the molecular skeleton in a perpendicular way. • Bulky side chains of spiro -IDT- O -IC to regulate its aggregation in blend films. • First report of a spiro-bridged ladder core used for A-D-A fused ring acceptors. [ABSTRACT FROM AUTHOR]