The ternary and tandem strategies are effective methods for improving the photovoltaic performance of organic solar cells (OSCs). Here an asymmetric wide-bandgap nonfullerene acceptor named AITC is synthesized. AITC with...

Main observation and conclusion Recently, the asymmetric nonfullerene acceptors (NFAs) with acceptor‐donor‐acceptor (A‐D‐A) structure have been developed rapidly, especially for the modification of asymmetric core, asymmetric side chains and asymmetric end groups. In this work, a novel asymmetric A‐D‐π‐A type NFA with a noncovalently fused‐ring core named PIST‐4F is synthesized, containing an indacenodithieno[3,2‐b]dithiophene (IDT), two strong electron‐withdrawing end groups and an alkylthio‐substituted thiophene π‐bridge. Benefiting from the S···S noncovalent interaction between the sulfur atom on π‐bridge and the adjacent thiophene in IDT, the PIST‐4F presents nearly planar geometry and extended conjugated area, resulting in the optimized electronic properties, charge transport, and film morphology compared to the symmetric NFA PI‐4F. As a result, PM6:PIST‐4F‐based devices achieve a higher power conversion efficiency (PCE) of 13.8%, while the PM6:PI‐4F‐based devices only show a PCE of 7.1%. Notably, the PM6:PIST‐4F‐based devices processed with nonhalogen solvent toluene exhibit an excellent PCE as high as 13.1%. These results indicate that PIST‐4F is an effective acceptor for high‐efficiency organic solar cells.

Ternary strategy by introducing a third component into the binary host system has been proven to be a simple and promising method to boost the power conversion efficiency (PCE) and...

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To develop high-efficiency polymer solar cells (PSCs), the acceptors in a bulk heterojunction (BHJ) blend are supposed to possess complementary absorption bands in the near-infrared region and a suitable energy level to be well-matched with the donors. In this work, a new small molecular acceptor (SMA) named IDTT8-N based on an indacenodithienothiophene (IDTT) core was designed and synthesized. In comparison to the counterpart molecule IDTN with an indacenodithiophene (IDT) core, IDTT8-N with the extended π-conjugation length of an IDT core not only exhibits a red shift of ca. 35 nm in optical absorption but also has little change on its lowest unoccupied molecular orbital (LUMO) energy level. Therefore, PSCs based on PM6:IDTT8-N exhibit a superior short-circuit current density (J sc) and high open-circuit voltage (V oc). Moreover, apart from the strong face-on molecular stacking, distinct end-group π–π stacking of IDTT8-N can be observed in the blends, facilitating the charge transport. Therefore, the optimized PM6:IDTT8-N-based devices exhibit dramatically high and balanced electron mobility (μe) and hole mobility (μh), whose magnitudes are over 10–3 cm2 V–1 s–1. Consequently, an extraordinary PCE of 14.1% with a relatively high J sc of 20.98 mA cm–2 and a V oc of 0.94 V was recorded. To our knowledge, it is the new record among PSCs with a SMA based on 2-(3-oxocyclopentylidene)­malononitrile (INCN) as end groups. These results indicate that extending the π-conjugation length of the fused ring core of a SMA is an efficient method to both enhance the absorption and the molecular interaction of the acceptor as well as the photovoltaic performance of PSCs.