Mechanistic Investigation into Dynamic Function of Third-Component Incorporated in Ternary Near-Infrared Nonfullerene Organic Solar Cells

Zhuoyan Wang, Jingjing Ji, Weihua Lin, Yao Yao, Kaibo Zheng, Ziqi Liang*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Organic solar cells (OSCs) consisting of an ultralow-bandgap nonfullerene acceptor (NFA) with an optical absorption edge that extends to the near-infrared (NIR) region are of vital interest to semitransparent and tandem devices. However, huge energy-loss related to inefficient charge dissociation hinders their further development. The critical issues of charge separation as exemplified in NIR-NFA OSCs based on the paradigm blend of PTB7-Th donor (D) and IEICO-4F acceptor (A) are revealed here. These studies corroborate efficient charge transfer between D and A, accompanied by geminate recombination of photo-excited charge carriers. Two key factors restricting charge separation are unveiled as the connection discontinuity of individual phases in the blend and long-lived interfacial charge-transfer states (CTS). By incorporation of a third-component of benchmark ITIC or PC71BM with various molar ratios, these two issues are well-resolved accordingly, yet in distinctly influencing mechanisms. ITIC molecules modulate film morphology to create more continuous paths for charge transportation, whereas PC71BM diminishes CTS and enhances electron transfer at the D/A interfaces. Consequently, the optimal untreated ternary OSCs comprising 0.3 wt% ITIC and 0.1 wt% PC71BM in the blend deliver higher J(SC) values of 21.9 and 25.4 mA cm(-2), and hence increased PCE of 10.2% and 10.6%, respectively.
Original languageEnglish
Article number2001564
JournalAdvanced Functional Materials
Volume30
Issue number31
Number of pages10
ISSN1616-301X
DOIs
Publication statusPublished - 2020

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