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Self‐Assembly of Selective Interfaces in Organic Photovoltaics
Author(s) -
Mauger Scott A.,
Chang Lilian,
Friedrich Stephan,
Rochester Christopher W.,
Huang David M.,
Wang Peng,
Moulé Adam J.
Publication year - 2013
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.201201874
Subject(s) - materials science , organic solar cell , polymer solar cell , photovoltaics , neutron reflectometry , energy conversion efficiency , chemical physics , chemical engineering , optoelectronics , polymer , scattering , neutron scattering , photovoltaic system , optics , small angle neutron scattering , composite material , ecology , physics , biology , engineering
The composition of polymer‐fullerene blends is a critical parameter for achieving high efficiencies in bulk‐heterojunction (BHJ) organic photovoltaics. Achieving the “right” materials distribution is crucial for device optimization as it greatly influences charge‐carrier mobility. The effect of the vertical concentration profile of materials in spin‐coated BHJs on device properties has stirred particularly vigorous debate. Despite available literature on this subject, the results are often contradictory and inconsistent, likely due to differences in sample preparation and experimental considerations. To reconcile published results, the influence of heating, surface energy, and solvent additives on vertical segregation and doping in polymer‐fullerene BHJ organic photovoltaics are studied using neutron reflectometry and near edge X‐ray absorption fine structure spectroscopy. It is shown that surface energies and solvent additives greatly impact heat‐induced vertical segregation. Interface charging due to Fermi level mismatch increases (6,6)‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM)‐enrichment at the BHJ/cathode interface. Current–voltage measurements show that self‐assembly of interfaces affects the open‐circuit voltage, resulting in clear changes to the power conversion efficiency.