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Reducing the confinement of PBDB-T to ITIC to improve the crystallinity of PBDB-T/ITIC blends

Abstract

The ordered aggregation of non-fullerene small molecular acceptors (SMAs) plays a key role in determining the charge transport and bimolecular recombination in polymer/SMAs solar cells. However, due to the asymmetric phase separation in many polymer/SMAs systems, the polymers are prone to form network first, which inhibits the molecular diffusion of SMAs, resulting in weak crystallinity of SMAs. Here, we demonstrate a sequent-crystallization method for high performance PBDB-T/ITIC solar cell with much improved crystallinity of ITIC. By tuning the sequence of thermal annealing (TA) and solvent vapor annealing (SVA), sequent-crystallization of ITIC and PBDB-T can be fine controlled to grow high crystalline ITIC and PBDB-T network. The crystallization kinetics results indicate that when the crystallization of ITIC occurred prior to the formation of the PBDB-T crystallized network, the crystallinity of ITIC is significantly improved due to high molecular diffusion. However, if the crystallization of PBDB-T occurred first, the diffusion of ITIC was restricted by the crystalline network of PBDB-T, resulting in a low crystallinity of ITIC. The enhanced crystallinity of ITIC is beneficial to the electron transport and suppressed the bimolecular recombination, which helps boost device performance from 8.14% to 10.95%. This work demonstrates that manipulation of crystallization sequence of donor and acceptor may be a key to further boost the efficiency of polymer/SMAs solar cells.

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Publication details

The article was received on 20 Jun 2018, accepted on 11 Jul 2018 and first published on 13 Jul 2018


Article type: Paper
DOI: 10.1039/C8TA05892J
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Reducing the confinement of PBDB-T to ITIC to improve the crystallinity of PBDB-T/ITIC blends

    Q. Liang, J. Han, C. Song, X. Yu, D. M. Smilgies, K. Zhao, J. Liu and Y. Han, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C8TA05892J

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