Issue 40, 2020

Donor–acceptor type conjugated copolymers based on alternating BNBP and oligothiophene units: from electron acceptor to electron donor and from amorphous to semicrystalline

Abstract

Donor–acceptor (D–A) type conjugated polymers are widely used in high-performance organic opto-electronic devices. In this work, we develop a series of D–A type conjugated polymers, P-nT (n = 1–5), based on alternating double B←N bridged bipyridine (BNBP) unit and oligothiophene units of various length. In P-1T, P-2T, P-3T, P-4T and P-5T, the D units are thiophene, bi-thiophene, tri-thiophene, tetra-thiophene and penta-thiophene, respectively. We find that the opto-electronic properties and thin film morphologies of the polymers can be substantially changed by the length of the oligothiophene units. From P-1T to P-5T, both the HOMO and LUMO energy levels of the polymers gradually upshift because of the electron-donating nature of oligothiophene units. P-1T, P-2T and P-3T can be used as electron acceptors in all-polymer solar cells, while P-4T and P-5T can work as electron donors in fullerene-based organic solar cells. In addition, with the increasing length of the oligothiophene units, the crystallinity of the polymers increased. P-1T and P-2T are amorphous, while P-3T, P-4T and P-5T show semicrystalline property in solid state. All-polymer solar cell with P-3T as the electron acceptor exhibits a power conversion efficiency (PCE) of 6.52% and the fullerene-based organic solar cells with P-5T as the electron donor exhibits a PCE of 5.79%. These results provide a molecular design guideline to rationally tune optical, electronic and crystalline properties of D–A type conjugated polymers.

Graphical abstract: Donor–acceptor type conjugated copolymers based on alternating BNBP and oligothiophene units: from electron acceptor to electron donor and from amorphous to semicrystalline

Supplementary files

Article information

Article type
Paper
Submitted
10 Aug 2020
Accepted
04 Oct 2020
First published
05 Oct 2020

J. Mater. Chem. A, 2020,8, 20998-21006

Donor–acceptor type conjugated copolymers based on alternating BNBP and oligothiophene units: from electron acceptor to electron donor and from amorphous to semicrystalline

J. Miao, H. Li, T. Wang, Y. Han, J. Liu and L. Wang, J. Mater. Chem. A, 2020, 8, 20998 DOI: 10.1039/D0TA07833F

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