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Realizing Over 13% Efficiency in Green‐Solvent‐Processed Nonfullerene Organic Solar Cells Enabled by 1,3,4‐Thiadiazole‐Based Wide‐Bandgap Copolymers
Author(s) -
Xu Xiaopeng,
Yu Ting,
Bi Zhaozhao,
Ma Wei,
Li Ying,
Peng Qiang
Publication year - 2018
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201703973
Subject(s) - materials science , band gap , energy conversion efficiency , crystallinity , organic solar cell , homo/lumo , solvent , absorption (acoustics) , open circuit voltage , acceptor , optoelectronics , organic chemistry , voltage , molecule , chemistry , polymer , physics , quantum mechanics , composite material , condensed matter physics
Two novel wide‐bandgap copolymers, PBDT‐TDZ and PBDTS‐TDZ, are developed based on 1,3,4‐thiadiazole (TDZ) and benzo[1,2‐b:4,5‐b′]dithiophene (BDT) building blocks. These copolymers exhibit wide bandgaps over 2.07 eV and low‐lying highest occupied molecular orbital (HOMO) levels below −5.35 eV, which match well with the typical low‐bandgap acceptor of ITIC, resulting in a good complementary absorption from 300 to 900 nm and a low HOMO level offset (≤0.13 eV). Compared to PBDT‐TDZ, PBDTS‐TDZ with alkylthio side chains exhibits the stronger optical absorption, lower‐lying HOMO level, and higher crystallinity. By using a single green solvent of o ‐xylene, PBDTS‐TDZ:ITIC devices exhibit a large open‐circuit voltage ( V oc ) up to 1.10 eV and an extremely low energy loss ( E loss ) of 0.48 eV. At the same time, the desirable high short‐circuit current density ( J sc ) of 17.78 mA cm −2 and fill factor of 65.4% are also obtained, giving rise to a high power conversion efficiency (PCE) of 12.80% without any additive and post‐treatment. When adopting a homotandem device architecture, the PCE is further improved to 13.35% (certified as 13.19%) with a much larger V oc of 2.13 V, which is the best value for any type of homotandem organic solar cells reported so far.