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Issue 7, 2020
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A 16.4% efficiency organic photovoltaic cell enabled using two donor polymers with their side-chains oriented differently by a ternary strategy

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Abstract

Effective ternary material systems are usually achieved using a donor/acceptor guest that is structurally similar to the donor/acceptor host to maintain the film-morphology of the host binary blend. In this study, we report an unprecedented ternary material system, PBDB-TF:PBDB-T-SF:Y6, in which PBDB-T-SF is selected as the donor polymer guest of the PBDB-TF:Y6 binary blend. The absorption spectra of both polymers are almost overlapped and their energy levels are similar. However, the side-chains between the host (PBDB-TF) and the guest (PBDB-T-SF) are oriented differently, which modulates the morphology of the polymer phases from nanoscale (10–20 nm) fine fibrils in the host binary blend to an interpenetrating mesoscale polymer-crowd (>100 nm) with reduced phase crystallinity in the ternary blend. As a result, the electrical properties of the active layer are greatly improved: the hole mobility increases more than the electron mobility, resulting in balanced hole and electron mobilities; the monomolecular and bimolecular recombinations are both reduced; the charge carrier extraction is faster and the trap-assisted recombination is reduced, resulting in a longer recombination lifetime of charge carriers (0.19 μs vs. 0.15/0.11 μs). All of these contribute to the concurrently increased device fill-factor and short-circuit current-density, and finally improved efficiency (16.4%). Solid-state 19F magic angle spinning nuclear magnetic microscopy is conducted to probe interaction between the host and guest donor polymers. This study demonstrates that mesoscale morphology such as the polymer-crowd induced by differently oriented side chains of the host–guest polymers can be a morphological feature of active layer toward high-efficiency organic photovoltaic cells.

Graphical abstract: A 16.4% efficiency organic photovoltaic cell enabled using two donor polymers with their side-chains oriented differently by a ternary strategy

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Supplementary files

Article information


Submitted
05 Dec 2019
Accepted
15 Jan 2020
First published
16 Jan 2020

J. Mater. Chem. A, 2020,8, 3676-3685
Article type
Paper

A 16.4% efficiency organic photovoltaic cell enabled using two donor polymers with their side-chains oriented differently by a ternary strategy

Y. Chang, T. Lau, P. C. Y. Chow, N. Wu, D. Su, W. Zhang, H. Meng, C. Ma, T. Liu, K. Li, X. Zou, K. S. Wong, X. Lu, H. Yan and C. Zhan, J. Mater. Chem. A, 2020, 8, 3676
DOI: 10.1039/C9TA13293G

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