Copper indium diselenide polycrystalline thin films of p, i and n-type electrical conductivity were grown using a one step electrodeposition process in a single bath. The bulk structure and the stoichiometry of the layers were determined using X-ray diffraction and X-ray fluorescence. The material composition was correlated with the electrical conductivity type variation, detected by the photoelectrochemical cell. Atomic force microscopy analysis showed copper-rich films deposited at low cathodic potentials (0.6V vs Ag/AgCl) are of spherical and granular morphology and the grain sizes were 0.3 to 0.5 mm, while stoichiometric CIS films deposited at (1.0V vs Ag/AgCl) have grain sizes of 0.1 to 0.4 mm. The initial studies of optoelectronic properties (Voc, Jsc and FF) of the four-layer solar cell devices (glass/FTO/n-CdS/n-CIS/i-CIS/p-CIS/Au) are presented.

CdTe thin films were potentiostatically electrodeposited from a non-aqueous electrolytic bath containing ethylene glycol. In order to dope the CdTe using an n-type dopant according to a proposed new model, varying concentrations of iodine were added into the electrolytic bath. The resulting materials were studied for structural, morphological, optical and electrical properties. Structural analysis indicated the formation of CdTe layers without other possible phases at a concentration of ~0.05 M of iodine in the bath. Optical absorption measurements have yielded a direct band gap value of 1.42±0.03 eV without showing any noticeable changes of the energy gap. Inclusion of iodine in CdTe layers have increased the electrical conductivity by a factor of 5, indicating the positive n-type doping effects. The diodes of FTO/CdS/CdTe/Au structures showed improved I-V characteristics indicating the presence of a high potential barrier of 1.20 eV with low ideality factors around 1.40. These results demonstrate a considerable reduction of active recombination and generation centres from the structure. Although the fill factors observed are low, for the studied batches in this project, remarkable improvement of short circuit current densities over 40 mA cm-2 were observed together with open circuit voltage values in the range 500 - 700 mV. Capacitance-voltage measurements indicate a formation of a fully depleted device, desirable for photovoltaic conversion.

This 20 page full colour report explains in simple terms the differences between the various photovoltaic technologies, and new products and building approaches. The report also presents expected energy yields of the different technologies in the UK as determined by the Environmental Change Institute's PV-Compare project. The guide forms an indispensible guide to academics, system designers, energy advisors and the interested public, and would also make a valuable teaching aid. The report can be ordered online from the ECI website.

This paper aims to provide an overview of heat recovery by thermophotovoltaics (TPV) from industrial high-temperature processes and uses the glass industry in the UK as an example. The work is part of a study of potential industrial applications of TPV in the UK being carried out by the Northumbria Photovoltaics Applications Centre. The paper reviews the relevant facts about TPV technology and the glass industry and identifies locations of use for TPV. These are assessed in terms of glass sector, furnace type, process temperature, impact on the existing process, power scale and development effort of TPV. Knowledge of these factors should contribute to the design of an optimum TPV system. The paper estimates possible energy savings and reductions of CO2 emissions using TPV in the glass industry.

Abstract. Making use of the authors' experimental results and the evidence available in the literature, an alternative model for glass/conducting glass/CdS/CdTe/metal solar cells has been formulated. This model explains the device behaviour in terms of a combination of a hetero-junction and a large Schottky barrier at the CdTe/metal interface. The main experimental observations available to date are described and compared with the currently assumed p-n junction model and this proposed new model. It is shown that the proposed model explains almost all the experimental results more satisfactorily. The paper describes the guidelines to further increase the performance efficiencies based on the new model. Following these new guidelines, the authors have fabricated improved devices producing open circuit voltage (Voc) values over 600 mV, fill factor (FF) values over 0.60 and the short-circuit current density (Jsc) values over 60 mA cm-2 for best devices. Although the Voc and FF could be further improved, the remarkable improvement of Jsc indicates the possibility of further development of multilayer graded band gap tandem solar cells based on CdS/CdTe system.

The PV-Compare project is a comparative test of commercially available photovoltaic technologies at two locations: in the UK and Mallorca, Spain. Double junction amorphous silicon products have been shown to give the greatest energy yields per manufacturer's declared kWp in Mallorca due to their good performance under high temperatures. Copper indium diselenide and double junction amorphous silicon give the greatest returns of energy in the UK due to their good spectral response to the blue wavelengths between 400 and 500 nm found under overcast skies. We also highlight the importance of matching the efficiency characteristics of the inverter to the climate. High efficiency at low power inputs is important for high system yields in the UK, whilst high efficiency at high power inputs is more important in sunnier climes.

The average photon energy (APE) is a useful environmental parameter for analysing spectral effects of amorphous silicon cells. Single junction cells have a higher spectral performance as light becomes more blue shifted. Double and triple junction cells have a maximum spectral performance when the absorption profile is matched to the received spectrum. Their performance drops off when the radiation is either red or blue shifted, as the current produced by a multijunction device is limited by the least productive junction. Such mismatch is statistically more likely, and therefore more pronounced, as the number of junctions in a device increases. The majority of energy received at the Loughborough, UK test facility is delivered at redder APEs than for the optimum spectral performance of amorphous silicon cells.

To date the majority of investigations into the performance of amorphous silicon photovoltaic systems have been limited to single sites, and therefore the conclusions from such studies are unlikely to be as generic as they might at first appear. This paper compares data collected from different systems across the world in Brazil, Hong Kong, Spain, Switzerland, and the United Kingdom. All systems have been operating for a number of years, and are employing double junction amorphous silicon devices of a similar age manufactured by RWE Solar. The data are analysed for performance variations reflecting the different climatic zones, and the variations are explained on the basis of operating temperature, incident irradiation and seasonal spectral shift.

It has been previously reported that variations in the spectral irradiance under which an amorphous silicon device operates can have a significant effect on its electrical performance, often contributing to enhanced system yields compared to crystalline-based systems. In this work, spectral irradiance data based on models and measurements taken at the Centre for Renewable Energy Systems Technology (CREST) in the UK are presented. These are input into electrical models for amorphous silicon devices incorporating different number of junctions in order to investigate the impact of changing spectral irradiation. The results can be classified broadly as primary effects, those accounting for the available spectrally useful irradiance and secondary effects that consider the effects of mismatched currents in the stacked cells of multi-junction devices. The modeled short circuit currents correlate well with measurements and are demonstrated as a useful tool for further investigation.

Solar cell overheating due to high irradiation levels is a significant problem facing concentrator systems. Some form of cooling is needed to maintain the highest possible performance of such systems. Liquid filters may be used to inhibit unwanted solar radiation from reaching the cell and thus limit cell operating temperatures. The perform-ance of the cooling will depend on the optical properties of the liquid filter applied, as illustrated in this paper on the basis of different filters. An ideal filter is identified and its effects on the systems are described. It is shown, on the basis of system modeling calculations, that cell perform-ance could be increased by up to 25% using an ideal filter. Such a system can reach an efficiency of 22% in a realistic working environment compared to a STC value of 16%. The absorbed part of the incident radiation can be used as a heat source, so adding to the potential value of the system.

The effect of varying spectrum on PV output is often underestimated in the case of amorphous silicon photovoltaic devices. This paper gives an indication of the order of magnitude of the seasonal variation of the useful irradiance in a maritime climate and also shows that this will involve a direct change in efficiency. This can be expected to be in the range of 15 percent around the annual average, thus explaining the seasonal performance. The spectral effects are investigated by distinguishing between a primary and a secondary effect. The primary effect is dependent on the availability of useful spectral irradiance while the secondary effect depends also on the spectral composition of the light in the useful range. It is shown that the secondary effect is especially significant for double junction devices.

Two identical 6.2 kWp arrays have produced 4,884 and 8,050 kWh of energy per year in Oxford, UK and Mallorca, Spain, respectively. Multi-junction amorphous silicon and copper indium diselenide technologies give the highest returns of energy per peak power. Amorphous silicon and CIS have good spectral response to blue wavelengths, and consequently operate more efficiently under overcast conditions. Amorphous silicon also performs well at high insolations because its large band gap renders it less susceptible to temperature effects. Crystalline silicon technologies perform relatively better under the lower temperatures found in the UK.