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Effects of Solvent Additives on Morphology, Charge Generation, Transport, and Recombination in Solution‐Processed Small‐Molecule Solar Cells
Author(s) -
Kyaw Aung Ko Ko,
Wang Dong Hwan,
Luo Chan,
Cao Yong,
Nguyen ThucQuyen,
Bazan Guillermo C.,
Heeger Alan J.
Publication year - 2014
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201301469
Subject(s) - materials science , chemical physics , photocurrent , phase (matter) , recombination , charge (physics) , solvent , acceptor , molecule , morphology (biology) , charge carrier , chemical engineering , small molecule , nanoscopic scale , nanotechnology , optoelectronics , chemistry , organic chemistry , condensed matter physics , biochemistry , physics , genetics , quantum mechanics , biology , engineering , gene
The effects of solvent additive (1,8‐diiodooctane (DIO)) on the morphology, charge generation, transport, and recombination in solution‐processed small‐molecule solar cells are studied and these parameters are correlated with device performance. In the optimum nanoscale morphology, which is processed with 0.4% DIO, the phase separation is large enough to create a percolating pathway for carrier transport, yet still small enough to form large interfacial area for efficient charge separation. Complete phase separation in this film reduces the interfacial defects, which occurs without DIO, and hence suppresses the monomolecular recombination. Moreover, balanced charge transport and weak bimolecular recombination lead to a high fill factor (72%). On the other hand, an excess amount of DIO (0.8%) in the solvent results in the over‐aggregation of the donor phase, which disturbs the percolating pathway of the acceptor phase and reduces the electron mobility. The over‐aggregation of the donor phase also shrinks the interfacial area for charge separation and consequently reduces the photocurrent generation.