Impact of Terminal End-Group of Acceptor-Donor-Acceptor-type Small Molecules on Molecular Packing and Photovoltaic Properties

Sang Woo Kim, Yu Jeong Lee, Young Woong Lee, Chang Woo Koh, Yeran Lee, Min Je Kim, Kin Liao, Jeong Ho Cho, Bumjoon J. Kim, Han Young Woo

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7 Citations (Scopus)

Abstract

In this study, we synthesized two acceptor-donor-acceptor (A-D-A)-type small molecules (SMs) (P3T4-VCN and P3T4-INCN) with different terminal end-groups (dicyanovinyl (VCN) and 2-methylene-3-(1,1-dicyanomethylene)indanone (INCN)) based on the 1,4-bis(thiophenylphenylthiophene)-2,5-difluorophenylene (P3T4) core that possesses high coplanarity because of intrachain noncovalent Coulombic interactions. We investigated the influence of terminal end-groups on intermolecular packing and the resulting electrical and photovoltaic characteristics. A small change in the end-group structure of the SMs induces a significant variation in the torsional structures, molecular packing, and pristine/blend film morphology. It is noteworthy that the less crystalline P3T4-INCN with tilted conformation is highly sensitive to post-treatments (i.e., additives and annealing) such that it permits facile morphological modulation. However, the highly planar and crystalline P3T4-VCN exhibits a strong tolerance toward processing treatments. After morphology optimization, the fullerene-based bulk-heterojunction solar cell of tilted P3T4-INCN exhibits a power conversion efficiency (PCE) of 5.68%, which is significantly superior to that of P3T4-VCN:PC 71 BM (PCE = 1.29%). Our results demonstrate the importance of the terminal end-group for the design of A-D-A-type SMs and their sensitivity toward the postprocessing treatments in optimizing their performance.

Original languageEnglish
Pages (from-to)39952-39961
Number of pages10
JournalACS Applied Materials and Interfaces
Volume10
Issue number46
DOIs
Publication statusPublished - 2018 Nov 21

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Keywords

  • A-D-A structure
  • Coulombic interaction
  • molecular planarity
  • organic solar cell
  • post-treatment

ASJC Scopus subject areas

  • Materials Science(all)

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