A layer of a metal-organic framework (SURMOF) was prepared on a thiol monolayer on Au. Charge transport across the insulating membrane could be established by using ferrocene as an immobilised redox mediator. Reversibility of the immobilisation and its role in the electrode kinetics are discussed.
Mixed thin films of donor‐ and acceptor‐type molecular semiconductors were prepared by physical vapour deposition and studied by conduction measurements in the dark during film growth and under illumination at three distinct wavelengths across the visible range of the solar spectrum. The molecules were chosen to provide both, good spectral coverage of the solar spectrum and appropriate differences in the electronic energy levels to allow charge carrier separation. Photocurrents were observed that indicated the expected contributions to the net photoconduction but also anomal, negative contributions were found, leading to a decreased conduction under illumination, showing the presence of isolated clusters. Ripening of the mixed films in vacuum and conditioning the films at air were studied subsequently and consequences on conduction and photoconduction discussed. The applicability of such films in evaporated organic bulk heterojunctions as photoconductors or in photovoltaic cells is discussed.
Vacuum chamber for simultaneous evaporation of pure and mixed organic thin films equipped with in situ (photo)‐conduction measurements.
The influence of the substrate temperature during film growth as well as annealing of films subsequent to preparation was studied by in situ measurements of conduction and photoconduction of molecular blends of phthalocyaninatocopper (PcCu) and buckminster-fullerene (C 60 ). The findings are discussed in context of structural and morphological changes observed in scanning electron microscopy (SEM) and UV/Vis transmission measurements. Deposition of bulk heterojunctions (BHJs) at elevated substrate temperature featured improved percolation pathways leading to increased conductivity, photoconductivity, and exciton dissociation yield. At low concentrations of PcCu in C 60 electron trapping by light-induced hole states in PcCu was observed.
Organic solar cells consisting of Phthalocyaninatocopper (PcCu) as donor and the Buckminsterfullerene C60 as acceptor molecule were prepared by physical vapor deposition as planar or bulk heterojunctions. The devices were studied by IV-characterization as well as intensity-modulated photovoltage spectroscopy to determine the average lifetime of charge carriers formed subsequent to light absorption. An increasing charge carrier lifetime was determined for an increasing PcCu-content in the films. Back transfer of electrons at the undesired contact of C60 with PEDOT:PSS as well as recombination following hole trapping in interface states in the contact of PcCu with C60 or in isolated domains of PcCu are discussed as possible origins.
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