Simple Nonfused Ring Electron Acceptors with 3D Network Packing Structure Boosting the Efficiency of Organic Solar Cells to 15.44%

Three nonfused ring electron acceptors (NFREAs; 2Th-2F, BTh-Th-2F, and 2BTh-2F) with thieno[3,2-b]thiophene bearing two bis(4-butylphenyl)amino substituents as the core, 3-octylthiophene or 3-octylthieno[3,2-b]thiophene as the spacer, and 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone as the terminal group are designed and synthesized. The molar extinction coefficient of acceptors and the electron mobility of blend films gradually increase with increasing pi-conjugation length. Moreover, 2BTh-2F displays a planar molecular conformation assisted by S center dot center dot center dot N and S center dot center dot center dot O intramolecular interactions. More importantly, the molecular stacking changes from 2D packing for the 2Th-2F analog to 3D network packing for 2BTh-2F. Due to these comprehensive merits, 2BTh-2F:PBDB-T-based organic solar cells give a high power conversion efficiency of 14.53%. More impressively, when D18 is used as the donor polymer, the power conversion efficiency is further enhanced to 15.44%, which is the highest value reported for solar cells based on NFREAs.

Automated summary

NFREAs with increasing pi-conjugation length show enhanced molar extinction coefficient and electron mobility in blend films. The molecular conformation of 2BTh-2F is planar, supported by S···N and S···O intramolecular interactions, and it forms a 3D network packing structure compared to the 2D packing of 2Th-2F. 2BTh-2F:PBDB-T-based organic solar cells achieve a high power conversion efficiency of 14.53%, reaching a record efficiency of 15.44% when D18 is used as the donor polymer.