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A Versatile Buffer Layer for Polymer Solar Cells: Rendering Surface Potential by Regulating Dipole
Author(s) -
Zhong Wei,
Chen Lie,
Xiao Shuqin,
Huang Liqiang,
Chen Yiwang
Publication year - 2015
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.201500500
Subject(s) - materials science , kelvin probe force microscope , cathode , optoelectronics , dipole , poling , anode , work function , electrode , ultraviolet photoelectron spectroscopy , auxiliary electrode , layer (electronics) , x ray photoelectron spectroscopy , analytical chemistry (journal) , nanotechnology , ferroelectricity , electrolyte , chemical engineering , atomic force microscopy , dielectric , chemistry , organic chemistry , chromatography , engineering
Spin‐coated film of poly(vinylidenefluoride‐hexafluoropropylene) (P(VDF‐HFP)) acts as a cathode/anode buffer layer in polymer solar cells (PSCs) with conventional/inverted device structures. Such devices show optimized performances comparable with the controlled device, making P(VDF‐HFP) a good substitute for LiF/MoO 3 as a cathode/anode buffer layer. Ultraviolet photoelectron spectroscopy (UPS) and Kelvin force microscope (KFM) measurements show that increased surface potential of active layers improves cathode contact. In piezoresponse force microscopy (PFM) measurement, P(VDF‐HFP) responds to applied bias in phase curve, showing tunable dipole. This tunable dipole renders surface potential under applied bias. As a result, open‐circuit voltage of devices alters instantly with poling voltage. Moreover, positive poling of P(VDF‐HFP) together with simultaneous oxidation of Ag gradually improves performance of inverted structure device. Integer charge transfer (ICT) model elucidates improved electrode contacts by dipole tuning, varying surface potential and vacuum level shift. Understanding the function of dipole makes P(VDF‐HFP) a promising and versatile buffer layer for PSCs.