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Focuses on a study which presented efficiency data of solar cells based on a soluble derivative of p-phenylene vinylene, poly-p-phenylene vinylene and methanofullerene embedded into polystyrene. Energy conversion efficiencies of various organic solar cells; Photoinduced electron transfer between conjugated polymers and fullerenes; Results and discussion; Conclusion.

With the spread of photovoltaics (PV) and increasing diversity in PV panel technology, quantitative comparison of the modules is highly desirable for consistent on-site quality assessment. Electroluminescence imaging reveals many defects, such as macroscopic crystal or electrical contact defects, but quantitative comparison outside the laboratory without controlled environment is still difficult, especially for different detector technologies. Here, we show how this problem can be addressed by adding reference spots in the module area: One passive dark spot and an active bright spot composed of a high-power back-contacted silicon PV cell. Those reference spots are used to evaluate the module's electroluminescence signal under different environmental conditions and to establish comparable results. Additionally, the comparison of images acquired with different camera technology detectors, such as silicon and InGaAs, is realised for signal levels. [ABSTRACT FROM AUTHOR]

Temperature accelerated lifetime measurements are applied to conjugated polymer based bulk heterojunction solar cells. The short circuit current under white light illumination is monitored over time for different temperatures, ranging from 40 °C to 105 °C. An Arrhenius type dependence of the degradation constant with temperature is observed and an activation energy E[sub a] of ∼350 meV is derived. [ABSTRACT FROM AUTHOR]

Several efforts on using a dye-sensitized TiO2 nanocrystalline solar cell (nc-DSC) by replacing the liquid electrolyte with a solid-state analogy (by either a polymer electrolyte or a hole conducting material) intend to eliminate practical problems with sealing and degradation. Polymeric materials that behave as hole conductors are of practical interest as replacements for the liquid electrolyte, since they are inexpensive and can be tailored chemically to fit a wide range of purposes. In this report, all solid-state organic/inorganic hybrid dye-sensitized solar cells were fabricated based on a bi- and tri-layer device concept using a transparent nanocrystalline TiO2 layer as the electron acceptor and transport layer, a surface-adsorbed RuL2(NCS)/TBA (2:2) dye complex for light absorption and electron injection to the conduction band of TiO2, and conjugated polymers as for the transport of holes to the back contact electrode. Comparative results of I–V characteristics, energy or power conversion efficiencies, as well as the surface network morphology of these films by atomic force microscope (AFM) will be discussed. [Copyright &y& Elsevier]

Abstract: Thermographic methods are widely established to detect shunts in photovoltaic technologies. In all methods the cell has to be directly accessible to determine quantitative shunt values. In this manuscript a precise method is presented to determine shunt values in solar modules consisting of series connected bulk-heterojunction organic solar cells without the need to access the single cells separately. It will be shown that, although parallel resistances in organic solar cells show a strong dependence on the illumination intensity, the shunts that are detected using illuminated lock-in-thermography are strongly ohmic and therefore can be assigned a distinct ohm value. [Copyright &y& Elsevier]

Abstract: CuInGaSe2 (CIGS) thin film solar modules, despite their high efficiency, may contain three different kinds of macroscopic defects referred to as bulk defects, interface defects and interconnect defects. This occurs due to film's sensitivity to inhomogeneities during the manufacturing process. The result is a decrease of electrical power output from a cell or module. In this paper, we present the influence of macroscopic defects on the electrical behavior of CIGS thin film solar cells. To accomplish this, we investigated the relation between the IR-signal emitted of a defect in a cell (measured using illuminated lock-in thermography ILIT) and the respective open circuit cell voltage (V oc,cell) under low light conditions (< 100W/m²). Furthermore, we developed a modified masking method of measuring V oc,cell of a single cell within a thin film solar module. [Copyright &y& Elsevier]

Abstract: The grain structure of thin-film silicon layers obtained by chemical vapor deposition and zone melting recrystallization (ZMR) on SiC barrier layers, as developed for thin-film solar cells, have been investigated by electron backscatter diffraction (EBSD). The occurrence of subgrain boundaries was checked by defect etching. Twin boundaries form 1 to 100μm wide stripes, which are nearly parallel to the scan direction of ZMR. We find that stripe structure and the dominant grain orientations differ significantly from previously published ZMR layers grown on SiO2 surface. In a comprehensive model it is shown how the twinning structure and the dominant grain orientation can be related to the growth kinetics. The electronic activity of the defects was measured by electron beam induced current (EBiC). Contrary to other defects, the twin boundaries show no enhanced recombination. Therefore the found growth regime has potential advantages with respect of electronic properties of the layers. [Copyright &y& Elsevier]

For efficiently harvesting the terrestrial solar spectrum in conjugated polymer based solar cells, low bandgap polymers with a bandgap <1.8 eV are needed. The photophysics of such low band gap conjugated polymers as well as their excited state interactions with electron acceptors such as fullerenes are of importance when using them in photovoltaic devices. In this work we present a device structural study on the soluble low bandgap polymer PTPTB, consisting of alternating electron-rich N-dodecyl-2,5-bis (2′-thienyl)pyrrole (TPT) and electron-deficient 2,1,3-benzothiadiazole (B) units. The bandgap of this polymer, determined by electrochemistry and by optical absorption, is 1.6 eV. The performance of the photovoltaic devices is discussed in terms of spectrally resolved photocurrent measurements, AM1.5 measurements and temperature dependent I–V spectroscopy. Strategies to utilize this polymer for bulk heterojunction tandem solar cells with either a wide band gap polymer or in conjunction with strongly absorbing small molecular dyes are discussed. [Copyright &y& Elsevier]

To obtain photovoltaic devices based on electron donating conjugated polymers with a higher efficiency, a major breakthrough was realised by mixing the polymers with a suitable electron acceptor, thereby enhancing the rate for photo-induced charge generation by several orders. State-of-the-art organic bulk hetero-junction photovoltaic cells are based on an interpenetrating donor–acceptor network in the bulk to form efficient nanostructured p–n junctions in the organic materials. Devices made with ‘Gilch’ poly(2-methoxy-5-(3′,7′-dimethyl-octyloxy))-p-phenylene vinylene, (MDMO-PPV), as an electron donor and (6,6)-phenyl-C61-butyric-acid (PCBM) (a soluble C60 derivative) as an electron acceptor yielded the highest efficiency until now in this class of devices. A power conversion efficiency of approximately ηe≥2.5% (electrical power out/incident light power) under AM 1.5 illumination was reported. The ‘gilch’ route is a direct synthetic route. The ‘sulphinyl’ route is a promising, indirect precursor-route towards MDMO-PPV. Due to the non-symmetric monomer, so-called ‘head-to-head’ and ‘tail-to-tail’ additions are excluded to a higher level in comparison to the ‘gilch’ route. This difference between both materials makes them interesting candidates to compare them in the state-of-the-art photovoltaic devices. Preliminary results indicate that the ‘sulphinyl’ MDMO-PPV/PCBM bulk hetero-junction solar cells attain a power conversion efficiency of nearly ηe=3% (electrical power out/incident light power), have a higher fill factor, incident photon per converted electron value (IPCE) and short circuit current. It is indicated that the observed solar cell characteristics are related to the defect level of the conjugated polymer used. [Copyright &y& Elsevier]