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Issue 44, 2018
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Aromatic end-capped acceptor effects on molecular stacking and the photovoltaic performance of solution-processable small molecules

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Abstract

Aromatic end-capped acceptors are important in constructing donor materials and non-fullerene acceptors in organic solar cells. However, their features (such as electron-withdrawing ability and subtle change in planarity) and effects on molecular stacking and photovoltaic performance, lack a systematic study. This manuscript reports four molecules, namely, BT-RCN, BT-BA, BT-RA, and BT-ID, which are terminated by different acceptors in the same backbone. We quantify the molecular planarity through their dipole moment in the Z direction and investigate the effect of the degree of planarity on molecular properties and device performances. The four acceptors are classified into two groups based on acceptor strength: medium-strong and strong acceptors. Molecules based on medium-strong acceptors exhibit excellent efficiencies as follows: 10.1% for BT-ID, 9.6% for BT-RA, and 8.5% for BT-BA. Their decreased efficiency is quite consistent with their lowered hole mobility. Grazing incidence X-ray diffraction results demonstrate the positive relationship between the non-planarity of the acceptors and d-spacing distance in the π–π stacking direction, which are detrimental to mobility. BT-RCN, with a strong acceptor, obtains the lowest efficiency of 6.1%. These findings indicate the importance of matching the electron-donating ability of donor units and electron-withdrawing ability of acceptor units, and the subtle planarity change in molecular properties and aggregation.

Graphical abstract: Aromatic end-capped acceptor effects on molecular stacking and the photovoltaic performance of solution-processable small molecules

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Publication details

The article was received on 03 May 2018, accepted on 08 Jun 2018 and first published on 15 Jun 2018


Article type: Paper
DOI: 10.1039/C8TA04102D
Citation: J. Mater. Chem. A, 2018,6, 22077-22085
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    Aromatic end-capped acceptor effects on molecular stacking and the photovoltaic performance of solution-processable small molecules

    D. Deng, Y. Yang, W. Zou, Y. Zhang, Z. Wang, Z. Wang, J. Zhang, K. Lu, W. Ma and Z. Wei, J. Mater. Chem. A, 2018, 6, 22077
    DOI: 10.1039/C8TA04102D

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