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Abstract The passivated emitter and rear cell (PERC), with advantages of reducing rear surface recombination and improving rear surface reflectivity, is extensively applied in monocrystalline and multicrystalline silicon solar cells. In this study, we investigated the rear PERC structure with various contact patterns (type I to VI) and line spacings (800–1000 µm) using 156.75 mm × 156.75 mm p-type Czochralski mono crystalline silicon wafers. The void formation on the rear-side contacts of PERC structures played an important role in affecting conversion efficiencies. A smaller laser ablated opening width may easily lead to the formation of voids under screen printing and co-firing backside aluminum. Further evidence from the electroluminescence (EL) measurements confirmed that the higher laser ablation power would result in a slightly dark region for the solar cell with a rear-side contact opening width greater than 45 µm. The type III backside contact pattern (dash 2:1) with a line spacing of 900 µm surpassed all other contact patterns owing to its excellent aluminum back surface field. As a result, by optimizing both the backside contact pattern and line spacing of PERC solar cells, the best conversion efficiency of 22.25% and 20.9% for the average PERC solar cells were achieved.

In this work, the NbTiSiN and NbTiSiON layers are used instead of NbTiN and NbTiON layers to further improve the thermal stability of Al/NbTiN/NbTiON/SiO2 multilayer solar selective absorbing coating. The thermal stability of Si-doped individual layers and multilayer coatings are investigated. The X-ray diffraction (XRD) results show that Si incorporation into NbTiN (NbTiSiN) layer does not change its preferred orientation, and the Si-doped NbTiON (NbTiSiON) layer remains in amorphous phase. On the other hand, by introducing Si into NbTiN and NbTiON layers induce significant improvement of the oxidation resistance at 500 °C in air. After ageing in air at 500 °C for 2 h, the absorptance and emittance (at 400 °C) of Al/NbTiN/NbTiON/SiO2 and Al/NbTiSiN/NbTiSiON/SiO2 multilayer coatings change from 0.934/0.13 and 0.931/0.12 to 0.538/0.14 and 0.922/0.13, respectively. Meanwhile the surface roughness increases from 18.3 and 7.9 to 41.5 and 14.7 respectively, as atomic force microscopy (AFM) shows. The Al/NbTiSiN/NbTiSiON/SiO2 coating still has a high absorptance (0.910) and low emittance (0.13, at 400 °C) after ageing at 550 °C in vacuum for 100 h. It displays that Si-doping play an important role in the improvement of the thermal stability.

The solar hybrid-wall is widely used in natural ventilation and air heating in buildings. This article aims to experimentally study the induced chimney effect in a solar hybrid double wall. The effect of the air ventilation gap width and solar radiation intensity on the temperature distribution and induced air flow rate at the outlet of the hybrid wall was investigated with a variable chimney gap width-to-height ratio between 1:10 and 3:5. The results demonstrated that a lowest temperature position exists in the air gap and the position varies with the width of the air gap. The average air velocity in the air gap increases with the strength of the radiation intensity, and it shows a peak value with decreasing chimney gap width. The induced mass flow rate increases with both the radiation intensity and the chimney gap width. The optimum chimney gap width-to-height ratio is around 0.2–0.3 according to the coupling effect of the temperature and the air volume. Smoke visualization experiment demonstrates that reverse flow occurs in solar chimneys with a gap width-to-height ratio bigger than 0.3. It was found that the prediction method available in the literature can be well applied to narrow chimneys with a gap width-to-height ratio less than 0.3.

Abstract Crystallinity, optical band gap, resistivity and photoresponse of thermally evaporated In2S3 thin films deposited at a temperature of 350 °C and further annealed in sulfur vapour at different temperature range of 200–300 °C is investigated. It is observed that with an increase of annealing temperature, predominantly β-In2S3 phase is formed and the optical band gap for indirect allowed transitions increases from 1.6 eV to 2.0 eV and for direct allowed transitions from 2.3 eV to 2.7 eV. The electrophysical properties indicate that the activation mechanism of conductivity with an activation energy in the range of 0.5–0.73 eV, which is typical for the presence of indium vacancies in the β-In2S3 crystal structure and for the replacement of sulfur by oxygen atoms. It is also noted that sulfur annealing at temperatures of 250–300 °C leads to an increase in the conductivity and photosensitivity of films, which is suitable for photovoltaic applications.

Abstract In this work, the scalable screen printing process has been adopted to prepare low-cost and earth-abundant tin selenide (SnSe) films to study as the counter electrode in dye-sensitized solar cells (DSSCs). The SnSe powder was synthesized by solid state reaction method and corresponding films were fabricated by screen printing technique. The electrocatalytic activity of SnSe for redox iodide/triiodide (I−/I3−) couple and charge transfer resistance at the CE/electrolyte interface were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The DSSC with SnSe counter electrode exhibited with power conversion efficiency (PCE) of ~5.76% with open-circuit voltage of 0.63 V and short circuit current density of 12.39 mA/cm2 whereas the DSSC with platinum counter electrode showed PCE of 8.09% with open-circuit voltage of 0.68 V and short circuit current density of 14.77 mA/cm2. Thus, earth abundant and low cost SnSe films fabricated by screen printing technique could be an alternative to costly platinum counter electrode in DSSC.

Solar energy technology and energy storage technology are promising to make a contribution to current energy and global climate issue. The energy demand of daily cooking is enormous, and conventional cooking methods use gas or electricity with large carbon emissions. This paper proposes an innovative solar cooking system (SCS) integrated with rock-bed thermocline storage. Thermal oils transfer heat from the collectors to the rocks in the charging process and release heat in cooktop unit for cooking. The energy consumption of a household is first assessed by a reasonable hypothesis. Mathematical models and simulation models are then established to analyze the heat transfer performance of the cooktop unit and the annual running performance of the SCS. The rock-bed thermocline storage, single-tank thermocline storage and two-tank storage are compared. The simulation results indicate that the rock-bed thermocline storage unit employed to SCS will enhance the annual running performance and acquire the minimum initial investment cost. The economic analysis shows that the lowest levelized cost of cooking energy (LCOC) of the SCS is 0.3884 $/kWh, while the corresponding levelized cost of cooking a meal (LCCM) is 0.953 $/Meal and the solar fraction (SF) is 71%. Compared to the electrical and natural gas cooker, the SCS saves 1.75 tons and 0.52 tons of carbon emissions annually, respectively.

Abstract PV module testing under standard conditions is an important and well-established procedure, which plays a vital role in module rating. However, PV modules rarely operate at standard conditions therefore their field performance should be predicted based on long term outdoor monitoring or by means of models – so called energy yield models, which combine PV module characteristics with varying environmental conditions. The present work employs a bottom-up, physics-based energy yield modelling approach, which accounts to the interacting optical, thermal and electrical mechanisms in a detailed manner. Additionally, measured data is used for the accurate calibration of the models. Such an approach permits to explore the influence of cell- and module technology details on energy yield under any specific environmental conditions. The present work employs such a method to evaluate the influence of Silicon solar cell technology on energy yield under desert and moderate climates, where the interplay of different irradiance and ambient temperature levels result in a challenging PV performance prediction problem. The purpose of this work is to identify the best-suited solar cell technologies and to understand the underlying mechanisms, which lead to superior PV performance under specific climate conditions. The study is performed by means of physics-based exploratory energy yield simulations with detailed resolution of the thermal effects. Our comparison of four different cell technologies in monofacial modules highlights that superior illumination-dependent performance can contribute to annual energy yield enhancement under both moderate and desert climates amounting to 1.75% and 0.4%, respectively; while a 0.04%/°C advantage in relative temperature coefficient increases annual energy yield (by 1.2%) only under a desert climate.