Highly Efficient All-Small-Molecule Organic Solar Cells with Appropriate Active Layer Morphology by Side Chain Engineering of Donor Molecules and Thermal Annealing

Beibei Qiu; Zeng Chen; Shucheng Qin; Jia Yao; Wenchao Huang; Lei Meng; Haiming Zhu; Yang Michael Yang; Zhi-Guo Zhang; Yongfang Li

doi:10.1002/adma.201908373

Highly Efficient All-Small-Molecule Organic Solar Cells with Appropriate Active Layer Morphology by Side Chain Engineering of Donor Molecules and Thermal Annealing

Adv Mater. 2020 May;32(21):e1908373. doi: 10.1002/adma.201908373. Epub 2020 Apr 9.

Authors

Beibei Qiu^{1

2}, Zeng Chen³, Shucheng Qin^{1

2}, Jia Yao⁴, Wenchao Huang^{5

6}, Lei Meng¹, Haiming Zhu³, Yang Michael Yang⁷, Zhi-Guo Zhang⁴, Yongfang Li^{1

2

8}

Affiliations

¹ Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
² School of Chemical Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
³ Center for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China.
⁴ College of Materials Science and Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, China.
⁵ State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, China.
⁶ Department of Materials Science and Engineering, Monash University, Clayton, VIC, 3168, Australia.
⁷ State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310027, China.
⁸ Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123, China.

PMID: 32270545
DOI: 10.1002/adma.201908373

Abstract

It is very important to fine-tune the nanoscale morphology of donor:acceptor blend active layers for improving the photovoltaic performance of all-small-molecule organic solar cells (SM-OSCs). In this work, two new small molecule donor materials are synthesized with different substituents on their thiophene conjugated side chains, including SM1-S with alkylthio and SM1-F with fluorine and alkyl substituents, and the previously reported donor molecule SM1 with an alkyl substituent, for investigating the effect of different conjugated side chains on the molecular aggregation and the photophysical, and photovoltaic properties of the donor molecules. As a result, an SM1-F-based SM-OSC with Y6 as the acceptor, and with thermal annealing (TA) at 120 °C for 10 min, demonstrates the highest power conversion efficiency value of 14.07%, which is one of the best values for SM-OSCs reported so far. Besides, these results also reveal that different side chains of the small molecules can distinctly influence the crystallinity characteristics and aggregation features, and TA treatment can effectively fine-tune the phase separation to form suitable donor-acceptor interpenetrating networks, which is beneficial for exciton dissociation and charge transportation, leading to highly efficient photovoltaic performance.

Keywords: all-small-molecule organic solar cells; interpenetrating networks; side-chain engineering; small molecule donor materials; thermal annealing.

Abstract

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