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Formation of Bulk Heterojunctions by Alternative Thermal Deposition and Its Structure Analysis for High Efficiency Small Molecular Organic Photovoltaics
Author(s) -
Kim Ji Whan,
Kim Hyo Jung,
Lee Hyun Hwi,
Kim Taemin,
Kim JangJoo
Publication year - 2011
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.201002601
Subject(s) - materials science , organic solar cell , heterojunction , grazing incidence small angle scattering , evaporation , deposition (geology) , energy conversion efficiency , thin film , nanometre , fullerene , absorption (acoustics) , polymer solar cell , chemical engineering , photovoltaics , optoelectronics , scattering , analytical chemistry (journal) , polymer , nanotechnology , optics , composite material , organic chemistry , photovoltaic system , ecology , chemistry , engineering , biology , paleontology , neutron scattering , thermodynamics , physics , sediment , small angle neutron scattering
We propose a new method to form small‐molecule based bulk heterojunctions (SM‐BHJs) through alternative thermal deposition (ATD), which is a simple modification of conventional thermal evaporation. By ATD, the thicknesses of alternative donor and acceptor layers are precisely controlled down to 0.1 nm, which is critical to form BHJs. The formation of a BHJ in copper(II) phthalocyanine (CuPc) and fullerene (C 60 ) systems is confirmed by atomic force microscopy (AFM), grazing incidence X‐ray small angle scattering (GISAXS), and absorption measurements. From analysis of the data, we find that the CuPc|C 60 films fabricated by ATD are composed of nanometer sized disk‐shaped CuPc nano grains and aggregated C 60 , which explains the phase separation of CuPc and C 60 . On the other hand, the co‐deposited CuPc:C 60 films do not show the existence of separated CuPc nano grains in the CuPc:C 60 matrix. The OPV cells fabricated using the ATD method show significantly enhanced power conversion efficiency compared to the co‐deposited OPV cells with the same composition.