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Regulating the morphology of fluorinated non-fullerene acceptor and polymer donor via binary solvent mixture for high efficiency polymer solar cells

DOI: 10.1007/s11426-019-9484-8 DOI Help

Authors: Mengxue Chen (Wuhan University of Technology) , Zhuohan Zhang (Nanjing University of Science and Technology) , Wei Li (Wuhan University of Technology) , Jinlong Cai (Wuhan University of Technology) , Jiangsheng Yu (Nanjing University of Science and Technology) , Emma L. K. Spooner (University of Sheffield) , Rachel C. Kilbride (University of Sheffield) , Donghui Li (Wuhan University of Technology) , Baocai Du (Wuhan University of Technology) , Robert S. Gurney (Wuhan University of Technology) , Dan Liu (Wuhan University of Technology) , Weihua Tang (Nanjing University of Science and Technology) , David G. Lidzey (University of Sheffield) , Tao Wang (Wuhan University of Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science China Chemistry , VOL 62 , PAGES 1221 - 1229

State: Published (Approved)
Published: September 2019
Diamond Proposal Number(s): 20419

Abstract: Fluorinated non-fullerene acceptors (NFAs) usually have planar backbone and a higher tendency to crystallize compared to their non-fluorinated counterparts, which leads to enhanced charge mobility in organic solar cells (OSCs). However, this self-organization behavior may result in excessive phase separation with electron donors and thereby deteriorate device efficiency. Herein, we demonstrate an effective approach to tune the molecular organization of a fluorinated NFA (INPIC-4F), and its phase separation with the donor PBDB-T, by varying the casting solvent. A prolonged film drying time encourages the crystallization of INPIC-4F into spherulites and consequently results in excessive phase separation, leading to a low device power conversion efficiency (PCE) of 8.1%. Contrarily, a drying time leads to fine mixed domains with inefficient charge transport properties, resulting in a moderate device PCE of 11.4%. An intermediate film drying time results in the formation of face-on π-π stacked PBDB-T and INPIC-4F domains with continuous phase-separated networks, which facilitates light absorption, exciton dissociation as well as balanced charge transport towards the electrode, and achieves a remarkable PCE of 13.1%. This work provides a rational guide for optimizing the molecular ordering of NFAs and electron donors for high device efficiency.

Journal Keywords: solvent; efficiency; morphology; organic solar cells; non-fullerene acceptors

Subject Areas: Chemistry, Materials, Energy

Instruments: I07-Surface & interface diffraction