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Alkynyl-functionalized pyrene-cored perylene diimide electron acceptors for efficient non-fullerene organic solar cells Feng Tang, Kaile Wu, Zhijie Zhou, Guo Wang, Bin Zhao, and Songting Tan ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.9b00611 • Publication Date (Web): 06 May 2019 Downloaded from http://pubs.acs.org on May 7, 2019
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Alkynyl-functionalized pyrene-cored perylene diimide electron acceptors for efficient non-fullerene organic solar cells Feng Tang, Kaile Wu, Zhijie Zhou, Guo Wang, Bin Zhao*, Songting Tan* Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan 411105, China E-mail:
[email protected](S. Tan),
[email protected] (B. Zhao)
ABSTRACT: Integrating two or more perylene diimide (PDI) monomer through the single bond or ring fusion forming a star-shaped structure is a useful strategy for designing high-efficiency electron acceptors. Herein, we implemented an effectual acetylene-linked method of constructing star-shaped PDI derivatives based highefficiency non-fullerene organic solar cells (OSCs). A rigid and conjugated pyrene-cored PDI acceptor, B-4TPDI, has been designed and synthesized. The new acceptor manifests favorable morphology, effective π-electron delocalization and complementary absorption when it is paired with the polymer donors PTB7-Th or PBDB-T. It is shown that OSCs based on PTB7-Th: B-4TPDI blend film achieved a power conversion efficiency (PCE) of 7.71 % and an outstanding Jsc of 18.13 mA cm-2. More importantly, after adding a small amount of B-4TPDI into PTB7-Th: ITIC and PBDB-T: ITIC system, the formed ternary OSCs obtained an optimized PCE of 8.76 % and 10.93%, respectively. Our work confirms that acetylene linkage would be a prospective π-spacer for designing conjugated PDI derivatives based new and excellent non-fullerene acceptors. KEYWORDS: Alkynyl-function; pyrene; perylene diimide; non-fullerene acceptor; organic solar cells. 1
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1. INTRODUCTION The vigorous developments of non-fullerene acceptors(NFAs) have injected new vitality into the field of organic solar cells (OSCs).1-9 OSCs have seen dramatic developments in power conversion efficiencies (PCEs) of up to 15%-17%, which benefits from the development of new NFAs.10-12 Two kinds of n-type materials, perylene diimides (PDI) and indacenodithiophene (IDT) based small molecular acceptors, were proposed to be promising candidates for the further breakthrough in terms of power conversion efficiency.13-20 PDI based small molecules often exhibit upshifting lowest unoccupied molecular orbital (LUMO) levels, leading to a high open-circuit voltage (Voc) even up to 1.26 V in non-tandem organic solar cells through a suitable molecular modification.21,22 Due to relatively weaker electron-deficiency lactimfused rings and intramolecular charge transfer (ICT), a majority of PDI based n-type materials display a narrower and short absorption band from 400~600 nm (wide-bandgap), compared to that of typical IDT based n-type materials from 600~800 nm (narrow-bandgap). In addition, in view of the large planar structure of PDI unit, a lot of researchers have devoted to synthesizing PDI acceptors by constraining two or more PDI units on a crowded core through the single bond or ring fusion to forma highly twisted molecular geometry which suppresses the strong aggregation behavior of the blend film.23-27 Indeed, the non-coplanar structure would yield smooth film morphology when it blends with the polymer donor, thus to enhance the exciton diffusion and charge separation. Nevertheless, the non-coplanar structure would depress the chargetransport ability of the NFAs and undermine the 2
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intramolecular charge transfer. Therefore, most of PDI based NFAs possess a narrow optical absorption (λonset
