Effect of the π-conjugation length on the properties and photovoltaic performance of A-π-D-π-A type oligothiophenes with a 4,8-bis(thienyl)benzo[1,2-<i>b</i>:4,5-<i>b</i>′]dithiophene core

Yin, Ni, Wang, Lilei, Lin, Yi, Yi, Jinduo, Yan, Lingpeng, Dou, Junyan, Yang, Hai-Bo, Zhao, Xin and Ma, Chang-Qi (2016) Effect of the π-conjugation length on the properties and photovoltaic performance of A-π-D-π-A type oligothiophenes with a 4,8-bis(thienyl)benzo[1,2-<i>b</i>:4,5-<i>b</i>′]dithiophene core. BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY, 12 (1). pp. 1788-1797.

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Abstract

Benzo[1,2-<i>b</i>:4,5-<i>b</i>']dithiophene (BDT) is an excellent building block for constructing π-conjugated molecules for the use in organic solar cells. In this paper, four 4,8-bis(5-alkyl-2-thienyl)benzo[1,2-<i>b</i>:4,5-<i>b</i>']dithiophene (TBDT)-containing A-π-D-π-A-type small molecules (COOP-<i>n</i>HT-TBDT, <i>n</i> = 1, 2, 3, 4), having 2-cyano-3-octyloxy-3-oxo-1-propenyl (COOP) as terminal group and regioregular oligo(3-hexylthiophene) (nHT) as the π-conjugated bridge unit were synthesized. The optical and electrochemical properties of these compounds were systematically investigated. All these four compounds displayed broad absorption bands over 350-600 nm. The optical band gap becomes narrower (from 1.94 to 1.82 eV) and the HOMO energy levels increased (from -5.68 to -5.34 eV) with the increase of the length of the π-conjugated bridge. Organic solar cells using the synthesized compounds as the electron donor and PC₆₁BM as the electron acceptor were fabricated and tested. Results showed that compounds with longer oligothiophene π-bridges have better power conversion efficiency and higher device stability. The device based on the quaterthiophene-bridged compound <b>4</b> gave a highest power conversion efficiency of 5.62% with a <i>V</i>_OC of 0.93 V, <i>J</i>_SC of 9.60 mA·cm^-2, and a FF of 0.63.

Item Type:	Article
Uncontrolled Keywords:	A-pi-D-pi-A-type conjugated molecules, benzodithiophene, pi-bridge, chain length effect, organic solar cell
Depositing User:	Symplectic Admin
Date Deposited:	11 Feb 2019 14:44
Last Modified:	16 Mar 2024 00:20
DOI:	10.3762/bjoc.12.169
Open Access URL:	https://www.beilstein-journals.org/bjoc/articles/1...
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3032660