Georgy L. Pakhomov

First tellurium-containing phthalocyanine analogues: strong effect of tellurium on spectral, redox and conductivity properties of porphyrazines with annulated chalcogenodiazole ring(s)

The first tellurium-containing phthalocyanine analogues have been prepared and spectroscopically characterised: the Mg(II) complex of tetra(1,2,5-telluradiazolo)porphyrazine and a low-symmetry tert-butyl substituted Mg(II) tribenzoporphyrazine with one fused 1,2,5-telluradiazole ring. It was observed that the introduction of Te atom(s) reduces the energy of the Q-transition, facilitates the reduction of the macrocycle and strongly increases the conductivity of thin films.

Rectification and NIR photoresponse in p-Si/phthalocyanine/metal heterostructures

Hybrid organic-on-inorganic heterostructures employing phthalocyanine molecular semiconductor and doped silicon were fabricated using standard microelectronic processes. Current-vs-voltage characteristics display rectifying behavior of such heterostructures, which becomes more pronounced if n-type phthalocyanine layer is utilized. Competitive influence of phthalocyanine/metal and phthalocyanine/p-Si interface on electrical transport in the devices is discussed. Heterostructures with lead phthalocyanine layer show photoconductive properties in the NIR domain when illuminated through p-Si side.

Properties of Josephson junctions in the inhomogeneous magnetic field of a system of ferromagnetic particles

The effect of a system of ferromagnetic particles on the field-dependent critical current of a Josephson junction is experimentally studied for junctions of different geometries. For edge junctions, the effect of commensurability between the periodic magnetic field of the particles and the Josephson vortex lattice is observed. The effect manifests itself in additional maxima of the field-dependent critical current. For overlap junctions, giant (greater than sixfold) variations of the maximum critical current are observed depending on the magnetic state of the particles. The changes in the “Fraunhofer” pattern of the overlaped Josephson junctions are attributed to the formation of Abrikosov vortices due to the effect of uniformly magnetized particles. The effects revealed in the experiments can be used to analyze the inhomogeneous magnetic field of a system of submicron particles and to control the transport properties of Josephson junctions.

Luminescence of phthalocyanine thin films

The near-IR luminescence in thin films of metal-free phthalocyanine and phthalocyanine complexes is investigated at room temperature. It is shown that the intensity of the luminescence peaks depends on the polymorphic modification and the structure of the complexes, whereas the peak positions remain virtually unchanged.

NO2 interaction with thin film of phthalocyanine derivatives {1}

Abstract Influence of nitrogen dioxide high pressures on copper phthalocyanines thin films has been studied by methods of electron- and IR-spectroscopy, quartz microbalance and parallel electroconductivity measurements. Peripheral substitution (chemical modification) of phthalocyanine macromolecule is forwarded for variation of properties of phthalocyanine films

Organic photovoltaic cells on polymeric substrates with buffer nanolayers

Prototypes of organic photovoltaic cells based on the planar “subphthalocyanine/fullerene” heterojunction were fabricated using flexible polymeric substrates. Current-vs-voltage characteristics in the dark and under illumination were recorded and basic photovoltaic parameters were derived. It was shown that introduction of the (top) barrier layer composed of Alq3 molecules under the cathode significantly lowers the parasitic resistances in the cells, so that fill factor rises up to 55%. If the (bottom) buffer InClPc layer is deposited onto the anode (ITO), then the open circuit voltage of cells increases from 0.47 to 0.83 V. The highest power conversion efficiency was achieved in OPVC with both top and bottom interfacial layers (∼1%).

Depth profiling of fullerene-containing structures by time-of-flight secondary ion mass spectrometry

A new variant of depth profiling for thin-film fullerene-containing organic structures by the method of time-of-flight (TOF) secondary ion mass spectrometry (SIMS) on a TOF.SIMS-5 setup is described. The dependence of the yield of C60 molecular ions on the energy of sputtering ions has been revealed and studied. At an energy of sputtering Cs+ ions below 1 keV, the intensity of C60 molecular ions is sufficiently high to make possible both elemental and molecular depth profiling of multicomponent (multilayer) thin-film structures. Promising applications of TOF-SIMS depth profiling for obtaining more detailed information on the real molecular composition of functional organic materials are shown.

Phthalocyanine-Based Schottky-Type Photovoltaic Cells with Magnetron Sputtered Al Electrodes

This work addresses the use of a sputtering technique for fabricating the top contacts to conventional sandwich-type ITO\phthalocyanine\Al cells. Current-vs-voltage characteristics of these cells measured both in dark and under illumination are compared with those of identical cells, but bearing a thermally evaporated Al cathode. The greatly improved efficiency is revealed in the former case: in particular, the fill factor increased by a factor of three.

Magnetron sputtered vs. thermally evaporated gold contacts in phthalocyanine-based thin film devices

Sandwich-type ITO/phthalocyanine/Au cells, where top gold contact was deposited by either thermal evaporation or magnetron sputtering, have been fabricated. Comparison of electrical characteristics of these cells revealed important distinctions, which are associated with the deposition method.

Tandem photovoltaic cells with a composite intermediate layer

We have fabricated and tested tandem photovoltaic cells containing series-connected subcells of the “oxide–organic semiconductor–metal” type. The organic semiconductors were two phthalocyanine dyes (SubPc and PcVO); Al or Ag:Mg were used as capping metallic electrodes. A semitransparent composite metal–oxide layer formed by molybdenum oxide MoOx deposited over an ultrathin Al layer is used to join the subcells. Additionally, a MoOx layer deposited onto glass/ITO substrates serves as an anode buffer in the front subcell, and LiF deposited onto the dye layers serves as a cathode buffer in the front or rear subcells. Upon optimization of the thickness and composition of the intermediate layer, the open circuit voltage Uoc amounts to 1.6 V reflecting total summation of the contributions from the each of the subcells at a wide spectral coating from 300–1000 nm. The fill factor in the tandem cell is not worse than in individually made single cells with the same scheme or in disconnected subcells.