Combining chlorination and sulfuration strategies for high-performance all-small-molecule organic solar cells

Three small-molecule donors based on dithieno[2,3-d:2',3'-d']-benzo[1,2-b:4,5-b'] dithiophene (DTBDT) unit were designed and synthesized by side chain regulation with chlorinated or/and sulfurated substitutions (namely ZR1, ZR1-Cl, and ZR1-S-Cl respectively), along with a crystalline non-fullerene acceptor IDIC-4Cl with a chlorinated 1,1-dicyanomethylene-3-indanone (IC) end group. Energy levels, molar extinction coefficients and crystallinities of three donor molecules can be effectively altered by combining chlorination and sulfuration strategies. Especially, the ZR1-S-Cl exhibited the best absorption ability, lowest higher occupied molecular orbital (HOMO) energy level and highest crystallinity among three donors, resulting in the corresponding all-small-molecule organic solar cells to produce a high power conversion efficiency (PCE) of 12.05% with IDIC-4Cl as an acceptor. (c) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

In this study, three small-molecule donors based on DTBDT unit were designed and synthesized, with chlorinated or/and sulfurated substitutions, along with a non-fullerene acceptor IDIC-4Cl. By combining chlorination and sulfuration strategies, energy levels, molar extinction coefficients, and crystallinities of donors can be effectively altered, with ZR1-S-Cl showing the best performance. The corresponding all-small-molecule organic solar cells achieved a high power conversion efficiency of 12.05% with IDIC-4Cl as an acceptor.