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Morphology and efficiency enhancements of PTB7-Th:ITIC nonfullerene organic solar cells processed via solvent vapor annealing

DOI: 10.1016/j.jechem.2018.12.015 DOI Help

Authors: Robert S. Gurney (Wuhan University of Technology) , Wei Li (Wuhan University of Technology) , Yu Yan (Wuhan University of Technology) , Dan Liu (Wuhan University of Technology) , Andrew J. Pearson (University of Cambridge) , Tao Wang (Wuhan University of Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Energy Chemistry , VOL 37 , PAGES 148 - 156

State: Published (Approved)
Published: October 2019

Abstract: The nanoscale morphology within the photoactive layer of organic solar cells is critical in determining the power conversion efficiency (PCE). Here, we draw attention to the roles of molecular arrangement, and domain size in improving performance, which can be tuned by subjecting the photovoltaic materials to solvent vapor annealing (SVA). In our PTB7-Th:ITIC devices, the PCE can be improved by exposing the device to solvent vapor for 60 s after solution casting. The solvent vapor prolongs reorganizational time and increases molecular ordering and domain size/phase separation, which are sub-optimal in pristine PTB7-Th:ITIC blend films. This improved morphology results in better charge mobility, reduced recombination, and ultimately an improved PCE from 7.1% to 7.9% when using CS2 as the annealing solvent. This simple SVA technique can be applied to a range of OPV systems where the molecular ordering is inferior within the as-cast photoactive layer.

Keywords: Polymer solar cells; Non-fullerene; Solvent vapor annealing

Subject Areas: Chemistry, Physics, Energy

Beamlines: I07-Surface & interface diffraction