Silicon Concentrator Solar Cells Research Articles

A spectrally splitting concentrating PV/T system using combined absorption optical filter and linear Fresnel reflector concentrator

A novel spectral splitting concentrating PV/T system (CPV) based on a combined absorption optical filter and a linear Fresnel reflector concentrator is developed. The combined absorption optical filter includes a selective absorbing liquid and a solid absorption filter, acting as a band pass filter for silicon concentrator solar cells. The optical performance of both the concentrator and the hybrid receiver under different conditions is investigated through ray tracing software-LightTools. The results show that the concentrated illumination distribution within the PV module width at the focal region of the concentrator is quite uniform and 72.15% of the spectral power in the spectral band 650–1075 nm incidents the PV module using light filtering by propylene glycol (PG) and HB650. Furthermore, an indoor test of a simplified receiver is conducted to verify the effectiveness of the combined absorption filter and an energy conversion performance of the proposed spectral splitting CPV/T system is evaluated. The use of PG and HB650 combined filter produces a higher total efficiency of 46.77% and yields economic value enhancement of 54% compared to the PV only system.

Facile preparation of core-shell Ag@SiO2 nanoparticles and their application in spectrally splitting PV/T systems

Several researchers have demonstrated that plasmonic nanofluids based filters can potentially enhance hybrid solar photovoltaic/thermal (PV/T) systems performance. In this work, we report a facile process for achieving silica-coated silver (Ag) nanoparticles using dimethylamine (DMA) as a basic solvent to induce tetraethyl orthosilicate (TEOS) hydrolysis. Then, the prepared Ag@SiO2 nanoparticles which have a controllable silica shell thickness are suspended in propylene glycol-CoSO4 hybrid fluid. Finally, the characteristics of the PV/T system filtered by the Ag@SiO2/CoSO4-PG nanofluids are evaluated based on the indoor test and photo-thermal conversion model. The results show that the nanoparticles prepared under optimized conditions, i.e., pH value of 8–9, water: ethanol volume ratio of 1:4, temperature of 25 °C, TEOS volume of 0.05 mL, and reaction time of 12 h, exhibit an absorption peak at 474 nm. Further, this study reveals that Ag@SiO2/CoSO4-PG nanofluid filter with concentration of 25.4 mg/L gives a reasonable spectral match with silicon concentrator solar cell according to the measured optical transmittance and the calculated filtering efficiency of 39.3%. The use of 25.4 mg/L Ag@SiO2/CoSO4-PG nanofluid filter produces a higher total efficiency of 63.3% and yields economic value enhancement of 67.8% compared to the PV only system when worth factor (w) is 3.

Investigation of CoSO4-based Ag nanofluids as spectral beam splitters for hybrid PV/T applications

Nanofluid can be used as an effective spectral beam splitter to enhance the performance of hybrid PV/T system. In this work, we innovatively developed CoSO4-based Ag nanofluid which might be utilized as fluid optical filter for hybrid PV/T system with silicon concentrator (CPV) solar cell. Firstly, highly dispersed Ag/CoSO4 nanofluids with various concentrations were prepared. The results from the measured optical transmittance of the prepared nanofluids show that Ag/CoSO4 nanofluid has a strong absorption over a broader spectrum than that of water-based one. Subsequently, the effect of Ag nanofluids filters on the electrical performance of the silicon CPV cell was discussed. Ag/CoSO4 nanofluids produce lower short circuit current and thus lower electrical output than Ag/water nanofluids at the same mass fraction of Ag nanoparticles, whereas they yield higher stagnation temperature than Ag/water nanofluids. A theoretical model for optimizing the optical properties of the nanofluids filters and determining merit function (MF) was introduced to evaluate the filtering performance of Ag/CoSO4 nanofluids in PV/T systems. The results show that the MF value of PV/T system with Ag/CoSO4-2 nanofluid filter is greater than both that with a typical Ag-SiO2 (core-shell)/water nanofluid filter and with a Ag/water nanofluid filter. And the calculated MF values for PV/T systems with Ag/CoSO4 nanofluid filters reach a nearly constant value higher than 1.371 when the mass fraction of Ag nanoparticles contained in the Ag/CoSO4 nanofluid ranging from 24 ppm to 57 ppm. Peak MF value is achieved when the mass fraction of Ag nanoparticles is 37 ppm.

Fluorine- and tin-doped indium oxide films grown by ultrasonic spray pyrolysis: Characterization and application in bifacial silicon concentrator solar cells

Multi-wire metallization and interconnection for silicon solar cells is considered as a revolutionary technology for the next generation of photovoltaic modules, since it drastically reduces their cost while boosting efficiency. In this paper, we report results obtained using an innovative approach for the fabrication of bifacial low-concentrator Ag-free Cz-Si (Czochralski silicon) solar cells based on an indium fluorine oxide (IFO)/(n+pp+)Cz-Si/indium tin oxide (ITO) structure. Transparent conducting oxide (TCO) layers, IFO and ITO, acting as antireflection electrodes, were grown by ultrasonic spray pyrolysis (USP). A copper wire contact pattern was attached by low-temperature lamination simultaneously to the front and rear TCO layers as well as to the interconnecting ribbons located outside the structure (laminated grid cell (LGCell) design). In this paper, to extend the operating range of sunlight concentration ratios of LGCells, the sheet resistance of the IFO and ITO layers has been reduced to 14 and 13Ω/sq, respectively, by increasing their thickness by about three times, from ∼85 to ∼240 nm. As a result, the operating range of the LGCells has been extended to 1–7suns. In the operating range, their front-illumination efficiency varies from 18.3 to 18.9% (back-illumination efficiency from 15.1 to 15.6%). We also report for the first time the results of systematic analysis of USP IFO properties and compare them with the USP ITO properties. The effect of the IFO thickness on grain size, electrical resistivity, charge carrier concentration and mobility, refractive index, transmission and absorption spectra, as well as optical band gap has been analyzed systematically by scanning electron microscopy, transmission and reflection spectra, optical ellipsometry and Hall measurements.

Cu₆Sn₅ Whiskers Precipitated in Sn3.0Ag0.5Cu/Cu Interconnection in Concentrator Silicon Solar Cells Solder Layer.

Cu6Sn5 whiskers precipitated in Sn3.0Ag0.5Cu/Cu interconnection in concentrator silicon solar cells solder layer were found and investigated after reflow soldering and during aging. Ag3Sn fibers can be observed around Cu6Sn5 whiskers in the matrix microstructure, which can play an active effect on the reliability of interconnection. Different morphologies of Cu6Sn5 whiskers can be observed, and hexagonal rod structure is the main morphology of Cu6Sn5 whiskers. A hollow structure can be observed in hexagonal Cu6Sn5 whiskers, and a screw dislocation mechanism was used to represent the Cu6Sn5 growth. Based on mechanical property testing and finite element simulation, Cu6Sn5 whiskers were regarded as having a negative effect on the durability of Sn3.0Ag0.5Cu/Cu interconnection in concentrator silicon solar cells solder layer.

New discovery of ZnO whisker in SnZn/Cu solder joints interconnection in concentrator silicon solar cells solder layer

In this work, we have found the formation of ZnO whiskers in SnZn/Cu solder joints interconnection in concentrator silicon solar cells solder layer. Different morphologies of ZnO whiskers were precipitated from rich-Zn phase. During oxidation, the diffusion of Zn atoms induces the formation of voids. The volume expansion (near surface zone) and volume shrinkage (inner zone) both appear in the microstructure matrix, and the tensile stress resulting from oxidation is the driving force for ZnO whisker growth. Net-type oxidation morphology along the triangular grain boundary resulting from that Zn diffuses onto the free surface along the grain boundaries of Sn was found synchronously.

Optimization of the Metal Finger of a Silicon Concentrator Solar Cell

The key factors affecting the efficiency of silicon concentrator solar cells with boron implanted emitters were investigated. It is found that, by optimization of the front metal finger, the efficiency of the solar cells can be improved by approximately 10% under 10 suns illumination with the finger spacing of 330 μm.

Direct liquid-immersion cooling of concentrator silicon solar cells in a linear concentrating photovoltaic receiver

Direct liquid-immersion cooling of solar cells using dimethyl silicon oil is proposed as a heat dissipation solution for linear CPV (concentrating photovoltaic) systems. To reduce the liquid holdup, a narrow rectangular channel receiver was designed and its heat transfer performance was investigated experimentally at an energy flux ratio of 9.1 suns. Long-term stability of mono-crystalline concentrator silicon solar cells immersed in dimethyl silicon oil with viscosity of 2 mm2/s was monitored under real climate conditions. Experimental results show that the liquid-immersion cooling capacity in the designed receiver is favorable. The cell temperature can be controlled in the range of 20–31 °C at a 910 W/m2 DNI (direct normal irradiance), 15 °C silicon oil inlet temperature and Re numbers (Reynolds) variation from 13,602 to 2720. The cell temperature distribution is quite uniform, and a general correlation of Nu number (Nusselt) was obtained. The electrical performance of the cells immersed in the silicon oil is stable and no obvious efficiency degradation was observed after immersed for 270 days.

Extraction of diode parameters of silicon solar cells under high illumination conditions

An analytical method has been developed to extract all four diode parameters, namely the shunt resistance, series resistance, diode ideality factor, and reverse saturation current density, using a single J–V curve, based on one exponential model of silicon solar cells under high illumination conditions. The slope of the J–V curve (dV/dJ) at a short circuit condition is used to determine the value of the shunt resistance. The slope of the J–V curve at an open circuit condition together with the short circuit current density, open circuit voltage, current density, and voltage at maximum power point have been used to determine the values of the series resistance, diode ideality factor, and reverse saturation current density. The determined values of the diode parameters have been used to compute the theoretical values of the open circuit voltage, curve factor, and efficiency of the solar cell. The theoretical J–V curves matched well with the corresponding experimental curves. This method is applied to determine the diode parameters of concentrator silicon solar cells at different illumination conditions in a temperature range of 298–323K. The computed values of the open circuit voltage, curve factor, and efficiency obtained using diode parameters determined with this method showed good agreement (<2% discrepancy) with the experimental values.

Understanding and Development of Screen-Printed Front Metallization for High-Efficiency Low-to-Medium Concentrator Silicon Solar Cells

This paper reports on a methodology to achieve low-cost high-efficiency screen-printed low-to-medium concentrator Si cells and validates it by fabricating some of the highest efficiency metal paste printed cells with a simple cell design. The model shows that the highest achievable efficiency at any given concentration is a function of metal paste, contact parameters, number of fingers, and finger length due to the tradeoff between resistive and shadow losses. Consistent with the model calculations, first, 52 mm × 27 mm ~19% cells were fabricated at ~5X (suns) with a Dupont 16 A paste and ~110 μm wide 32 lines. Then, with improved 50 μm wide direct extrusion printed fingers, >20% efficient cells were achieved in the concentration range of 3-16X, along with a roadmap to ~21% efficient cells. This approach provides excellent guidelines to design grid pattern and selecting cell dimensions to achieve maximum efficiency at the desired concentration from a given printing technology and cell structure.

Improving Silicon Concentrator Solar Cells Performance by Dielectric Liquids Immersion

Direct liquid immersion cooling of concentrator solar cells was proposed as a solution for receiver thermal management of concentrating photovoltaic (CPV) systems. This research investigates the electrical performance of silicon concentrator solar cells under concentration, which are in both the absence of the candidate immersion liquids and also within different thickness on top. The results show that the presence of thin liquid layers results in an increase in the silicon CPV solar cells efficiencies by 8.5-15.2% from the reference value, arising from a decrease in a part of the reflected radiation and a decrease in the velocity of the surface recombination from surface adsorption of polar molecules. With an increase in the thickness of the liquid layer, the degree of the improvements to the efficiencies of the cells decreases due to more incident light is absorbed by the thicker liquid layer, which also depends to a noticeable degree on the liquid species.

The performance and long-term stability of silicon concentrator solar cells immersed in dielectric liquids

Direct liquid-immersion cooling of concentrator solar cells was proposed as a solution for receiver thermal management of concentrating photovoltaic (CPV) systems. This research investigates the performance and long-term stability of silicon CPV solar cells operated in De-ionized (DI) water, isopropyl alcohol (IPA), dimethyl silicon oil, and ethyl acetate, respectively. Current–voltage characteristics of silicon CPV solar cells are measured. The presence of a thin liquid layer (1.5mm) results in an increase in the silicon CPV solar cells efficiency by 8.5–15.2% from the reference value. With an increase of the liquid layer thickness above the cell surface up to 9mm, due to more incident light is absorbed by the thicker liquid layer, the degree of the improvements to the cell efficiency decreases, which also depends to a noticeable degree on the liquid species. Further, more power output from the cells operated in liquids is achieved under higher concentration ratio. The long-term cell performance is discussed through three separate liquid immersion tests. The results from 1.5mm test demonstrate that degradation of cells performance immersed in IPA and in ethyl acetate mainly occurs by a decrease of Jsc and efficiency during 170days of test. But the long-term organic liquids immersion test (180days) without silicone sealant involved gives confidence of the reliable performance of the silicon CPV solar cells operated in liquids except for DI water. Therefore, the observed performance decay of the cells in 1.5mm test is due to the interaction between the silicone sealant and IPA or ethyl acetate. However, long-term immersion results from 9mm test (100days) show that the stable electrical performance of the cell is difficult to be achieved when immersed in DI water, which is consistent with the previous report.

Paleo-Dneister Holocene history: use of palynostratigraphy to assess the validity of dating by amino acid racemisation and C-14 ages of Black Sea shells

The problems of worldwide energy shortage and environment pollution are becoming more and more serious, thus lots of attention has been paid to renewable and sustainable energy. The development of photovoltaic technology was rapid in recent years as one of the promising renewable energy, the worldwide total amount of photovoltaic power plants had reached nearly 100 GW in 2012, and about 90% of the worldwide solar cells are crystalline silicon solar cells. But there is still a large gap between the electricity costs of photovoltaic and traditional fossil energy, lots of methods have been tried to decrease the costs. The efficiency of the cell could be increased by concentration, and parts of the solar cells are replaced by cheaper optical elements in concentration photovoltaic, thus the costs of photovoltaic could be decreased by concentration. The traditional solar cells used for concentration were III–V multi-junction solar cells, their costs were high although they had high efficiency, thus people tried to use cheaper silicon solar cells for concentration to decrease the costs further. In this work, six kinds of silicon solar cells with different structures used for concentration were summarized; the device structures, manufacturing processes and efficiencies of the cells were compared. The prospects of concentrator silicon solar cells were predicted, the Si HIT cell using back contact structure, the multi-junction cell containing Si back contact cell and the Si VMJ cell used with Ge and GaP VMJ cells were considered to have good potential in low, middle, high and very high concentration photovoltaic.

Development and Understanding of High-Efficiency Screen-Printed Concentrator Silicon Solar Cells

Concentrator cells have the potential to reduce the usage of semiconductor material while producing high efficiency and more power density in a cell. Silicon solar cells now provide a unique opportunity for low-cost concentrator systems that are suitable for low to medium (2-20X) concentration because cell technology and screen-printed contacts have improved considerably. In this paper, we report on the understanding and development of low-cost manufacturable screen-printed concentrator solar cells. Computer modeling was performed first to show that, under 10% metal coverage, it is possible for screen-printed cells to have series resistance that is low enough (<;0.29 Ω·cm2) to maintain high efficiency at low to medium concentrations. This was validated by design and fabrication of 40.56-cm2 screen-printed cells using an industrial feasible process that achieved 18.8% peak efficiency at ~6 suns and 17.2% efficiency at 20 suns. Dicing a 9.9-cm2 cell, which reduces the line resistance, raised the peak efficiency to 18.9% at 10 suns and 18.5% at 20 suns. Model calculations are performed to quantitatively establish the requirements for ~20% screen-printed 2-20X concentrator cells.

Mechanism study of the electrical performance change of silicon concentrator solar cells immersed in de-ionized water

Direct de-ionized (DI) water immersion cooling has been verified to be an effective method of managing the operating temperature of silicon solar cells under concentration. However, the stable electrical performance is difficult to be achieved. Possible factors from bare cell self, materials for tabbing cells were investigated in this study for understanding the degradation mechanism. Long term immersion results showed that no significant degradation on bare cells operated in DI water at 65 °C. When cells were tabbed using lead-based solder and flux, the short circuit current ( I sc ) of cells decreased with exposure time, notably under sunlight, but it was not observed for cell open circuit voltage ( V oc ). The epoxy tabbed cells test also demonstrated that the tabbed cells without lead-based solder and flux involved were also found drop in I sc , but with slower rate. The presence of lead and tin black oxides on the lead based-soldered tabbed cells and red deposition on the epoxy tabbed cells confirmed the occurrence of galvanic corrosion. However, particular cleaning recovers the I– V towards its initial values for the former tabbed cells, and partial recovery for the latter tabbed cells, which indicates that the cells are not damaged after long-time DI water immersion.

Reliability assessment of silicone coated silicon concentrator solar cells by accelerated aging tests for immersing in de-ionized water

Abstract Direct de-ionized (DI) water immersion cooling has been verified to be an effective method for managing the operating temperature of silicon solar cells under concentration. However, the stable electrical performance was difficult to be achieved. The following investigation on mechanism indicated that galvanic corrosion occurred on cells. In this study, silicone coating was proposed to apply for the silicon concentrator (CPV) solar cells to eliminate or minimize the degradation when operated in DI water for a long time. The reliability of the selected silicone coatings and the silicone coated silicon CPV cells was assessed through designed accelerated aging tests, which include damp heat test, thermal cycling test and DI water immersion test. The selected silicone coatings exhibited excellent optical transparency. The tests results showed that no issues related with the selected silicone coatings’ reliability were observed. Some variations in the electrical performance of the silicone coated cells were detected, but the results gave confidence of the reliable performance of coated cells since they represented less than the total degradation allowed for the module under these tests. The simulation results indicated that temperature of the coated cell in DI water can be still maintained lower than that of conventionally encapsulated cell.

Electrical and thermal performance of silicon concentrator solar cells immersed in dielectric liquids

Direct liquid-immersion cooling of concentrator solar cells was proposed as a solution for receiver thermal management of concentrating photovoltaic (CPV) and hybrid concentrating photovoltaic thermal (CPV-T) systems. De-ionized (DI) water, isopropyl alcohol (IPA), ethyl acetate, and dimethyl silicon oil were selected as potential immersion liquids based on optical transmittance measurement results. Improvements to the electrical performance of silicon CPV cells were observed under a range of concentrations in the candidate dielectric liquids, arising from improved light collection and reduced cell surface recombination losses from surface adsorption of polar molecules. Three-dimensional numerical simulations with the four candidate liquids as the working fluids, exploring the thermal performance of a silicon CPV cell array in a liquid immersion prototype receiver, have been performed. Simulation results show that the direct-immersion cooling approach can maintain low and uniform cell temperature in the designed liquid immersion receiver. The fluid inlet velocity and flow mode, along with the fluid thermal properties, all have a significant influence on the cell array temperature.

3D Analysis of the performances degradation caused by series resistance in concentrator solar cells

This paper deals with the modeling of series resistance components in silicon concentrator solar cells. The main components of the macroscopic series resistance are analyzed by means of one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) numerical simulations. It is shown that the contribution of the lateral current flux, flowing along the emitter region, and of the transverse current flux, flowing along the metal grid, cannot be neglected and, hence, the operation of solar cells subjected to high current densities cannot be described by simple one-dimensional models. The percentage weight of 2D and 3D components on the total value of the series resistance is evaluated and rules for the proper design of the cell geometries are given. An analysis of the effectiveness of the most popular methods for the extraction of the series resistance from the I–V curves of solar cells is also proposed.

Pilot production of concentrator silicon solar cells: Approaching industrialization

Using a simple process, high-efficiency silicon concentrator solar cells have proved to achieve up to 21% efficiency at 100×. The purpose of this work is to prove the feasibility of their industrialisation by setting up a pilot line and manufacturing a significant number of cells for a 100× concentrator system. The process has been successfully verified by modifying the antireflection coating, the annealing process and the back contact. This yielded an average efficiency of 18.5% at 100× with 70% of cells having an efficiency >18% and costs ranging from 0.31 to 0.41 €/W. A fast learning curve is shown which suggests optimistic results indeed for further industrialisation.

Thermophotovoltaic power generation systems using natural gas-fired radiant burners

Thermophotovoltaic (TPV) power generation in gas-fired furnaces is attracting technical attention. Considerable work has been done in the area of low bandgap GaSb cell-based TPV systems as well as silicon solar cell-based TPV systems. Previous investigations have shown that a radiant burner with a high conversion level of fuel to radiation energy must be developed to realize an efficient TPV system. In our work, we investigated different natural gas-fired radiant burners in order to raise the conversion of fuel energy to thermal radiation. These burners were used as radiation sources to establish and test two TPV prototype systems. It was found that for a non-surface combustion radiant burner, the radiation output can be enhanced using a thermal radiator with a porous structure. Also, we developed a cascaded radiant burner that generates two streams of radiation output. One stream illuminates silicon concentrator solar cells while the other drives low bandgap GaSb cells. In this way, useful radiation output and thus TPV system efficiency are significantly increased due to the cascaded utilization of combustion heat and optimized thermal management.