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Nonhalogen Solvent‐Processed Asymmetric Wide‐Bandgap Polymers for Nonfullerene Organic Solar Cells with Over 10% Efficiency
Author(s) -
An Yongkang,
Liao Xunfan,
Chen Lie,
Yin Jingping,
Ai Qingyun,
Xie Qian,
Huang Bin,
Liu Feng,
Jen Alex K.Y.,
Chen Yiwang
Publication year - 2018
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.201706517
Subject(s) - materials science , organic solar cell , fullerene , acceptor , thiophene , band gap , energy conversion efficiency , substituent , steric effects , polymer , homo/lumo , polymer solar cell , solvent , molecule , organic chemistry , composite material , optoelectronics , chemistry , physics , condensed matter physics
Two new wide‐bandgap D–A–π copolymer donor materials, PBDT‐2TC and PBDT‐S‐2TC, based on benzodithiophene and asymmetric bithiophene with one carboxylate (2TC) substituent are synthesized by a facile approach for fullerene‐free organic solar cells (OSCs). The combination of one carboxylate‐substituted thiophene with one thiophene bridge in the backbone substantially reduces the steric hindrance, thereby favoring a planar geometry for efficient charge transport and molecular packing. A reasonable highest‐occupied‐molecular‐orbital energy level in relation to that of the acceptor and balanced hole and electron transport are observed for both polymers. This asymmetric structure unit is flexible and versatile, allowing the absorption, energy levels, and morphology of the blend films to be tailored. Fullerene‐free OSCs based on PBDT‐S‐2TC:ITIC achieve a high power conversion efficiency of 10.12%. More impressively, a successful nonhalogen solvent‐processed solar cell with 9.55% efficiency is also achieved, which is one of the highest values for a fullerene‐free OSC processed using an ecofriendly solvent.