Aggregation Tuning with Heavily Fluorinated Donor Polymer for Efficient Organic Solar Cells

Xiao Kang; Xiaoming Li; Haining Liu; Zezhou Liang; Weichao Chen; Nan Zheng; Shanlin Qiao; Renqiang Yang

doi:10.1021/acsami.0c10658

Aggregation Tuning with Heavily Fluorinated Donor Polymer for Efficient Organic Solar Cells

ACS Appl Mater Interfaces. 2020 Nov 4;12(44):49849-49856. doi: 10.1021/acsami.0c10658. Epub 2020 Oct 26.

Authors

Xiao Kang^{1

2}, Xiaoming Li^{1

2}, Haining Liu¹, Zezhou Liang³, Weichao Chen², Nan Zheng⁴, Shanlin Qiao¹, Renqiang Yang⁵

Affiliations

¹ College of Chemistry and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China.
² College of Textiles & Clothing, State Key Laboratory of Bio-Fibers and Eco-Textiles, Collaborative Innovation Center for Eco-Textiles of Shandong Province, Qingdao University, Qingdao 266071, China.
³ School of Materials Science and Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China.
⁴ State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China.
⁵ Key Laboratory of Optoelectronic Chemical Materials and Devices (Ministry of Education), School of Chemical and Environmental Engineering, Jianghan University, Wuhan 430056, China.

PMID: 33103902
DOI: 10.1021/acsami.0c10658

Abstract

The fluorination/sulfofication-induced effect in the photovoltaic polymer solar cells (PSCs) needs to be paid much attention. In this work, a new donor polymer PBDB-PS2F was synthesized by heavily fluorinated and decorated S atom on the side chain of benzo[1,2-b:4,5-b']dithiophene (BDT) unit to explore the internal combined effect of F&S on the photoelectric performance. It was found that the heavy fluorination on the side chain could make PBDB-PS2F achieve a low highest occupied molecule orbital (HOMO) energy level of -5.72 eV and weaken the torsion of the main chain and effectively increase the intermolecular π-π* transition. Encouragingly, compared with the counterpart polymer PBDB-PS without the fluorination, PBDB-PS2F exhibited a much intense aggregation at room temperature but showed a tendency of reduced aggregation at high temperatures. This feature gives excellent solution processability and uniform morphology in the active layer of a PBDB-PS2F-based device, enabling an outstanding photovoltaic performance with the power conversion efficiency (PCE) of 13.56% (V_OC = 0.90 V, J_SC = 21.53 mA/cm², FF = 69.68%). Compared with that of the counterpart polymer PBDB-PS with no heavy fluorination, the V_OC of PBDB-PS2F increased by 15.4% and the PCE increased by 30.9%. Thus, the heavy-fluorination-induced effect to construct photovoltaic polymers could be used to improve the performance of polymer solar cells.

Keywords: heavily fluorinated; high open-circuit voltage; photovoltaic performance; polymer solar cell; solvent vapor annealing; temperature-dependent aggregation.