The complex refractive index of fluorinated subphthalocyanines (SubPcs) deposited by vacuum sublimation is determined by spectral ellipsometry. Their performance as acceptor material is characterized in a range of donor/acceptor heterojunctions in organic photovoltaic cells (OPVCs) by current–voltage measurements under 1 sun AM 1.5D simulated solar illumination and spectral response. Both electron and hole transfer between donor and acceptor materials is demonstrated. Power conversion efficiencies of 0.96% are found with an open‐circuit bias of 940 mV. Hence, it is shown that fluorinated SubPcs can be considered as an acceptor material in OPVCs with an absorption in the visible comparable to that of well‐known metallophthalocyanines.
The effect of bathocuproine (BCP) on the optical and electrical properties of organic planar heterojunction photovoltaic cells is quantified by current–voltage characterization under 1 sun AM 1.5D simulated solar illumination and spectral response at short‐circuit conditions. By inserting a 10 nm BCP layer in an indium tin oxide (ITO)/subphthalocyanine (SubPc)/buckminsterfullerene (C60)/BCP/Al thin‐film structure, an increase in power‐conversion efficiency from 0.05 to 3.0% is observed, mostly reflected in the enhanced open‐circuit voltage up to 920 mV. Furthermore, the incorporation of a 10‐nm BCP layer in an ITO/C60/BCP/Al structure leads to an increase in built‐in potential from 250 to 850 mV, as demonstrated by electroabsorption. It is argued that BCP passivates C60 such that a 10‐nm layer provides a sufficient buffer layer that prohibits Al contacting the C60 where it would otherwise create donor states.
Ultra‐thin films of subphthalocyanine (SubPc) were grown onto Si/SiO2 substrates by organic molecular beam deposition and the complex refractive index has been characterized by spectroscopic ellipsometry. The peak maximum in the extinction coefficient is determined to be 1.6 at 590 nm and the dielectric constant equals 3.9 in the limit of long wavelength. These values are extraordinary high when compared to the well‐known metal‐phthalocyanines and will be beneficial for the performance in a photovoltaic cell. The amorphous SubPc structure on top of indium‐tin‐oxide (ITO) as well as quartz glass is imaged by atomic force microscopy and scanning electron microscopy and we have characterized the nearly flat surface topology. Next, subphthalocyanine films in combination with buckminsterfullerene (C60) have been studied in a planar bilayer donor/acceptor heterojunction by current density‐voltage characterization under AM 1.5 simulated illumination at various light intensities. A power conversion efficiency of 3.0 % under 1 sun was measured. Finally, the external and internal quantum efficiencies demonstrated peak maxima at 590 nm of 46 % and 55 %, respectively. Considering the abrupt junction at the donor/acceptor interface, the electron transfer from SubPc to the acceptor material is thus determined to be highly efficient.
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