Conjugated Oligothiophene Derivatives Based on Bithiophene with Unsaturated Bonds as Building Blocks for Solution-Processed Bulk Heterojunction Organic Solar Cells

Chaohua Cui; Yue Wu; Man-Sing Cheung; Cheuk-Lam Ho; Qingchen Dong; Zhenyang Lin; Yongfang Li; Wai-Yeung Wong

doi:10.1002/asia.201601281

Conjugated Oligothiophene Derivatives Based on Bithiophene with Unsaturated Bonds as Building Blocks for Solution-Processed Bulk Heterojunction Organic Solar Cells

Chem Asian J. 2016 Dec 19;11(24):3557-3567. doi: 10.1002/asia.201601281. Epub 2016 Nov 25.

Authors

Chaohua Cui^{1

2}, Yue Wu², Man-Sing Cheung³, Cheuk-Lam Ho¹, Qingchen Dong⁴, Zhenyang Lin³, Yongfang Li², Wai-Yeung Wong^{1

5}

Affiliations

¹ Institute of Molecular Functional Materials, Department of Chemistry and Institute of Advanced Materials, Hong Kong Baptist University, Waterloo Road, Kowloon Tong, Hong Kong, P.R. China.
² Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P.R. China.
³ Department of Chemistry, The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong, P.R. China.
⁴ MOE Key Laboratory for Interface Science and Engineering in Advanced Materials, Research Center of Advanced Materials Science and Technology, Taiyuan University of Technology, 79 Yingze West Street, Taiyuan, 030024, P.R. China.
⁵ Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, P.R. China.

PMID: 27860355
DOI: 10.1002/asia.201601281

Abstract

A new building block ATVTA that uses stiff carbon-carbon triple bonds (A) on 1,2-di(2-thienyl)-ethene (TVT) has been developed. Oligothiophene derivatives S-01 with a TVT unit, S-02 with a 5,5'-diethynyl-2,2'-dithienyl (AT2) unit and S-03 with ATVTA were synthesized to compare their effects in a systematic study. Due to the better π-conjugation extension of the TVT unit, S-01 exhibits the most red-shifted absorption profile among them, whereas S-02 possesses the deepest HOMO level. While the HOMO level of S-03 is down-shifted by 0.02 eV relative to that of S-01, the alkyne linkages can effectively down-shift the HOMO level. By replacing the terminal units of S-03 with stronger electron acceptors, S-04 and S-05 exhibited broader absorption profiles and lower HOMO levels than those of S-03. Organic solar cells based on these molecules were fabricated and an S-03:PC₆₀ BM (1:1, w/w) based device afforded the highest V_oc value of 0.96 V and a power conversion efficiency (PCE) of 2.19 %.

Keywords: alkynes; conjugation; oligothiophenes; organic solar cells; synthesis.