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Mechanistic Investigation into Dynamic Function of Third Component Incorporated in Ternary Near‐Infrared Nonfullerene Organic Solar Cells
Author(s) -
Wang Zhuoyan,
Ji Jingjing,
Lin Weihua,
Yao Yao,
Zheng Kaibo,
Liang Ziqi
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202001564
Subject(s) - materials science , organic solar cell , ternary operation , acceptor , charge carrier , charge (physics) , optoelectronics , tandem , chemical physics , polymer , chemistry , computer science , physics , composite material , programming language , quantum mechanics , condensed matter physics
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 PC 71 BM 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 PC 71 BM 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% PC 71 BM 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.