Chlorinated Benzo[1,2-b:4,5-c']dithiophene-4,8-dione Polymer Donor: A Small Atom Makes a Big Difference.

ABSTRACT: The position of a chlorine atom in a charge carrier of polymer solar cells (PSCs) is important to boost their photovoltaic performance. Herein, two chlorinated D-A conjugated polymers PBBD-Cl-? and PBBD-Cl-? are synthesized based on two new building blocks (TTO-Cl-? and TTO-Cl-?) respectively by introducing the chlorine atom into ? or ? position of the upper thiophene of the highly electron-deficient benzo[1,2-b:4,5-c']dithiophene-4,8-dione moiety. Single-crystal analysis demonstrates that the chlorine-free TTO shows a ?-? stacking distance (d _?-?) of 3.55 Å. When H atom at the ? position of thiophene of TTO is replaced by Cl, both ?-? stacking distance (d _?-? = 3.48 Å) and Cl···S distance (d _Cl-S = 4.4 Å) are simultaneously reduced for TTO-Cl-? compared with TTO. TTO-Cl-? then showed the Cl···S non-covalent interaction can further shorten the intermolecular ?-? stacking separation to 3.23 Å, much smaller than that of TTO-Cl-? and TTO. After blending with BTP-eC9, PBBD-Cl-?:BTP-eC9-based PSCs achieved an outstanding power conversion efficiency (PCE) of 16.20%, much higher than PBBD:BTP-eC9 (10.06%) and PBBD-Cl-?:BTP-eC9 (13.35%) based devices. These results provide an effective strategy for design and synthesis of highly efficient donor polymers by precise positioning of the chlorine substitution.

SUBMITTER: Chao P 

PROVIDER: S-EPMC7887605 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature