Optics

Physics

Absorption (acoustics)

Yield (engineering)

HOMO/LUMO

Composite material

Organic chemistry

Band gap

Chemistry

Metallurgy

Materials science

Energy conversion efficiency

Pyrrole

Molecule

Bathochromic shift

Optoelectronics

Polymer

Polymer solar cell

Photochemistry

Organic solar cell

Fluorescence

National Science Review

Rationally utilizing and developing synthetic units is of particular significance for the design of high-performance non-fullerene small-molecule acceptors (SMAs). Here, a thieno[3,2-b]pyrrole synthetic unit was employed to develop a set of SMAs (ThPy1, ThPy2, ThPy3 and ThPy4) by changing the number or the position of the pyrrole ring in the central core based on a standard SMA of IT-4Cl, compared to which the four thieno[3,2-b]pyrrole-based acceptors exhibit bathochromic absorption and upshifted frontier orbital energy level due to the strong electron-donating ability of pyrrole. As a result, the polymer solar cells (PSCs) of the four thieno[3,2-b]pyrrole-based acceptors yield higher open-circuit voltage and lower energy loss relative to those of the IT-4Cl-based device. What is more, the ThPy3-based device achieves a power conversion efficiency (PCE) (15.3%) and an outstanding fill factor (FF) (0.771) that are superior to the IT-4Cl-based device (PCE = 12.6%, FF = 0.758). The ThPy4-based device realizes the lowest energy loss and the smallest optical band gap, and the ternary PSC device based on PM6:BTP-eC9:ThPy4 exhibits a PCE of 18.43% and a FF of 0.802. Overall, this work sheds light on the great potential of thieno[3,2-b]pyrrole-based SMAs in realizing low energy loss and high PCE.

Heteroheptacene-based acceptors with thieno[3<i>,</i>2-<i>b</i>]pyrrole yield high-performance polymer solar cells

Heteroheptacene-based acceptors with thieno[3,2-b]pyrrole yield high-performance polymer solar cells