Efficiency improvement of CIGS solar cells using RF sputtered TCO/Ag/TCO thin-film as prospective buffer layer

In this paper, TCO (Transparent Conductive Oxide) incorporating ultrathin Ag intermediate film is proposed as a new buffer layer to enhance the efficiency of CIGS thin-film solar cells (TFSCs). In this regard, versatile multilayer thin-films based on ZnO/Ag/ZnO and ITO/Ag/ITO structures were deposited on glass using RF magnetron sputtering technique to determine the optoelectronic parameters of the multilayer structures. The elaborated samples were then characterized using SEM, EDS, XRD, and UV–Visible absorption spectroscopy techniques to investigate the structure morphological, optical, and electronic properties. The deposited multilayer thin-films showed amorphous-like structure and exhibited a broadband absorbance over the visible and even NIR spectrum ranges, indicating its potential application as alternative buffer layers for thin-film solar cells. In this context, TCO/Ag/TCO/CIGS solar cells have been numerically investigated using the deposited multilayer optoelectronic properties. It was revealed that the estimated efficiency of the ZnO/Ag/ZnO/CIGS-based solar cell could reach 18.5% with an open circuit voltage of 0.7 V and a short-circuit current density of 34.8 mA/cm². The performances exhibited by the investigated solar cell demonstrated that ZnO/Ag/ZnO multilayer can be used as an alternative to the conventional CdS buffer layer for developing high-performance non-toxic CIGS solar cells.     

Dopant-free small molecule hole transport materials based on triphenylamine derivatives for perovskite solar cells

In the past decade, perovskite solar cells have become a promising candidate in the photovoltaic industry owing to their high power conversion efficiency that surpasses 25%. However, there are certain limitations that have hindered the development and full-scale practical application of these cells, including the high cost and degradation of perovskite caused by the dopants. Hence, there is an urgent need to develop dopant-free hole transport materials (HTMs). In recent years, HTMs based on triphenylamine (TPA-HTMs) are receiving growing interest owing to their high hole mobility, excellent film formation, and suitable energy levels. The literature here covers work relevant to TPA-HTMs in the last five years. They have been classified according to different core types. The correlations between performance and structure are summarized, and the future development trend of TPA-HTMs is highlighted.     

Economics of small solar-assisted multiple-effect stack distillation plants

The objective of this paper is to compare the economics of using solar energy to operate small, multiple-effect seawater distillation systems in remote areas with the conventional method of using fossil fuels. The particular multiple-effect system used is an advanced horizontal-tube, falling-film system called “multiple-effect stack” (MES) in which the pumping energy requirement is relatively low compared with the horizontal in-line system. Three system configurations were investigated: (1) a conventional system using a steam generator to provide steam for the MES evaporator and a diesel generator to provide pumping power, (2) a solar-assisted system which uses solar thermal collectors to provide hot water (instead of steam) for the evaporator and a diesel generator for pumping power, and (3) a solar stand-alone system which uses solar thermal collectors for the evaporator heat requirement and a solar PV array to provide electrical energy for pumping. At the present time, solar energy cannot compete favorably with fossil energy, particularly under the present international market prices of crude oil. However, in many remote sunny areas of the world where the real cost of fossil energy can be very high, the use of solar energy can be an attractive alternative. Two important cost parameters affect the relative economics of solar energy vis-à-vis conventional (fossil) energy: the collector cost in dollars per square meter and the cost of diesel oil in dollars per giga Joule. Solar energy becomes more competitive as the local cost of procuring conventional fuel increases and as the collector cost decreases. The water cost from a solar thermal-diesel-MES system (configuration #2) can be seen to approach the water cost from a steam generator-diesel-MES system (configuration #1) when the collector cost drops to $200/m² and diesel oil cost at the remote site reaches $50/GJ. Using a 100% solar system (configuration #3) with solar thermal and solar PV collectors, the economics was seen to improve in favor of the solar system. Even when diesel fuel can be procured at $10/GJ at the remote site, the cost of water from the solar system can be seen to approach that from a conventional plant when thermal collectors costing $200/m² are used. The cost of water from the solar system was shown to be always less than that from a conventional system which uses diesel oil procured at the high price of $50/GJ, but always higher than water produced from a conventional system using diesel oil at the low price of $10/GJ.     

A highly productive basin-type-multiple-effect coupled solar still

A newly designed multiple-effect solar still with a triangle cross-section consisting of a horizontal basin liner, a tilted double glass cover and the vertical parallel partitions in contact with saline-soaked wicks is presented and theoretically analyzed. Solar radiation is absorbed in the basin and in the first partition, and the partition section recycles the energy from the basin as well as solar energy, which is directly absorbed by the first partition. A single distillation cell with a 5-mm diffusion gap between vertical partitions has been experimentally explored. No contamination of distillate with saline water was experimentally detected in the single distillation cell, and the experimental observation of the wick and the measurements of the temperature drop through the cell with the 5-mm gap showed that dry patches hardly appear on the wick. The proposed still with 5-mm diffusion gaps is theoretically predicted to produce distillate of 15.4kg⁻² m⁻²d⁻¹ on a sunny day of G_ti=22.4 MJ/m⁻²d⁻¹ solar radiation, and its efficiency is about 3.5 times larger than the average experimental value for the conventional basin type stills by Cooper [20] and 1.2-1.6 times larger than the experimental maximum values of the conventional multiple-effect stills [3,9].     

Optimising solar photocatalytic mineralisation of pesticides by adding inorganic oxidising species; application to the recycling of pesticide containers

This paper focuses on optimising the use of additional oxidants in the photocatalytic degradation of a complex mixture of 10 commercial pesticides. The CPC solar pilot plant used for the tests has 8.9 m² of collector surface and a total volume of 247 l. Same total organic carbon (TOC) quantities of each pesticide were added to achieve the desired initial TOC concentration in all the experiments (from 5 to 100 mg of TOC l⁻¹). Experiments were performed with H₂O₂ and S₂O₈²⁻, but only peroxydisulphate was chosen for optimisation, because better results have been obtained with it. In addition to the consumption of the oxidant under different experimental conditions, the effect of peroxydisulphate and TOC concentrations was also evaluated. The mechanism of peroxydisulphate action is discussed with these results. The effect of reusing water and catalysts has also been studied. The results obtained from these experiments have been used to decide the dimensions and operating conditions of a solar photocatalytic plant, the final objective of which is the treatment of rinsates produced by washing pesticide containers.     

Degradation of atrazine using metalloporphyrins supported on TiO2 under visible light irradiation

A combined solar photo-Fenton and biological treatment is proposed for the decontamination of a mixture of five commercial pesticides commonly used in intensive agriculture Vydate (10% Oxamyl), Metomur (20% Methomyl), Couraze (20% Imidacloprid), Ditimur-40 (40% Dimethoate) and Scala (40% Pyrimethanil). Photo-Fenton experiments were conducted in a solar pilot reactor consisting of four compound parabolic collectors in which the pesticide mixture was treated at an original dissolved organic carbon (DOC) concentration of 200 mg/L in the presence of Fe²⁺ or Fe³⁺ concentration of 5, 20 and 55 mg/L. Ferrous ions were marginally more active than ferric in terms of active ingredient degradation, which followed zero order kinetics, more so in the early reaction stages. Photo-Fenton was also far more effective (by at least two orders of magnitude) than the respective dark reaction under identical experimental conditions.Irradiation for 50–100 min (normalized at 30 W/m² light intensity) at 20 mg/L Fe²⁺ was able to completely eliminate the active ingredients, and reduce DOC by about 15–50% and COD by 40–70%, respectively. At these conditions, ecotoxicity to the marine bacteria V. fischeri was substantially lessened, while aerobic biodegradability in tests with activated sludge was enhanced.     

Synergistic effect of TiO2 and iron oxide supported on fluorocarbon films: Part 2: Long-term stability and influence of reaction parameters on photoactivated degradation of pollutants

The degradation of hydroquinone (HQ) and nalidixic acid (NA) mediated by TiO₂ and iron oxide immobilized on functionalized polyvinyl fluoride films (PVF^f–TiO₂–Fe oxide) in the presence of H₂O₂ under simulated solar light has been examined. The results show that the contribution of homogeneous photo-Fenton oxidation to the initial mineralization process was low. The degradation rates were not dependant of initial pH. Heterogeneous photocatalytic activity of PVF^f–TiO₂–Fe oxide was enhanced by increasing temperature, NaCl addition and by long-term utilization.The PVF^f–TiO₂–Fe oxide surface was characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) at different states of utilization. Correlations between the catalyst surface composition and degradation kinetics are discussed. Long-term stability evaluated by repetitive pollutant degradations was outstanding. The presence of TiO₂ seems to (i) limit contact between polymer film and highly reactive radicals in the solution and (ii) act as a charge trap. Moreover, during the photocatalysis mediated by PVF^f–TiO₂–Fe oxide, some leaching of supported iron increased the amount of the top TiO₂ layer exposed to the light increasing the synergistic effects between the two oxides leading to enhanced pollutant degradation.     

Evaporative heat loss and heat transfer for open- and closed-cycle systems of a floating tilted wick solar still

An analytical expression for the thermal efficiency of evaporative heat loss and heat transfer for a open- and closed-cycle systems of floating tilted wick solar stills in terms of system design and climatic parameters has been derived. The expression for open- and closed-cycle systems was validated by performing experiments for both systems. Optimization of the design of the still for evaporative cooling (open cycle) and the distillation unit (closed cycle) was obtained using the derived analytical expression for large-scale installation. Numerical calculations were also carried out for a typical summer day at the Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore, India, to predict the performance of the still.     

太阳辐照度绝对辐射计的光电不等效性修正

针对绝对辐射计光电不等效性来源复杂、实验测量难度大的特点,提出了修正太阳辐照度绝对辐射计(SIAR)光电不等效性的有限元单元法。结合SIAR的测量方法,对真空中辐射计的腔温响应进行了实验测试。基于有限元单元法,建立了与实验腔温度响应相对误差仅为0.14%的有限元模型,对接收腔的温度响应进行了实验测试。测试结果显示:入射光功率为73.8mW时,接收腔与热沉之间的温度差异约为0.85K,响应的时间常数为29.8s。运用建立的有限元模型对SIAR的光电不等效性进行了评估和修正。结果表明:太阳辐照度绝对辐射计的光电不等效性来源主要为不同加热途径和不同加热区域引起的偏差,SIAR的光电不等效性因子N为0.999 621±0.000 004。该修正模型完善了仪器的修正体系,提高了测量精度,为绝对辐射计的发展提供了可靠的数据来源。