Crystalline-silicon solar cells have dominated the photovoltaics market for the past several decades. One of the long standing challenges is the large contribution of silicon wafer cost to the ...overall module cost. Here, we demonstrate a simple process for making high-purity solar-grade silicon films directly from silicon dioxide via a one-step electrodeposition process in molten salt for possible photovoltaic applications. High-purity silicon films can be deposited with tunable film thickness and doping type by varying the electrodeposition conditions. These electrodeposited silicon films show about 40 to 50% of photocurrent density of a commercial silicon wafer by photoelectrochemical measurements and the highest power conversion efficiency is 3.1% as a solar cell. Compared to the conventional manufacturing process for solar grade silicon wafer production, this approach greatly reduces the capital cost and energy consumption, providing a promising strategy for low-cost silicon solar cells production.
Electrodeposition of Si films from a Si‐containing electrolyte is a cost‐effective approach for the manufacturing of solar cells. Proposals relying on fluoride‐based molten salts have suffered from ...low product quality due to difficulties in impurity control. Here we demonstrate the successful electrodeposition of high‐quality Si films from a CaCl2‐based molten salt. Soluble SiIV−O anions generated from solid SiO2 are electrodeposited onto a graphite substrate to form a dense film of crystalline Si. Impurities in the deposited Si film are controlled at low concentrations (both B and P are less than 1 ppm). In the photoelectrochemical measurements, the film shows p‐type semiconductor character and large photocurrent. A p–n junction fabricated from the deposited Si film exhibits clear photovoltaic effects. This study represents the first step to the ultimate goal of developing a cost‐effective manufacturing process for Si solar cells based on electrodeposition.
Creating cheaper solar cells: High‐quality Si films for photovoltaic applications were fabricated by electrodeposition from molten CaCl2–CaO–SiO2. Soluble SiIV−O anions generated from solid SiO2 are electrodeposited onto a graphite substrate to form a dense and thick film of p‐type Si. Impurities in the deposited Si film are controlled at low concentrations. The film exhibits good photoelectrochemical properties and clear photovoltaic effects.
•An indirect method to calibrate a reference electrode.•Three methods to determine Li+/Li electrode potential.•Determination of AgCl/Ag electrode potential versus Cl2/Cl−.•Applicability in fluoride ...melts.
In this work, an innovative method was utilized to determine the AgCl(1% mol)/Ag reference electrode potential versus Cl2/Cl− at 673 K. Instead of directly measuring the chlorine electrode potential, the AgCl(1% mol)/Ag electrode potential versus Cl2/Cl− was calculated from the decomposition voltage of LiCl and the equilibrium potential of Li+/Li versus AgCl(1% mol)/Ag in a LiCl-KCl melt. The decomposition voltage of LiCl in the LiCl-KCl melt was calculated using the Nernst equation and the equilibrium potential of Li+/Li was determined by chronopotentiometry, open circuit chronopotentiometry and potentiodynamic scan techniques, and the deviation is within 5 mV. The AgCl(1% mol)/Ag electrode potential was determined to be −1.130 V vs Cl2/Cl− at 673 K. Since it does not involve direct injection of chlorine gas, this method is more convenient and safer than existing approaches. Furthermore, it also has the potential to be used to calibrate reference electrodes in a variety of melts.
Micro/nanostructured Zn and Cu–Zn alloy films have been electrodeposited directly from ZnO/CuO precursors in ChCl/urea-based DES, the typical nucleation-growth mechanism and the ...micro/nanostructures-formation process are determined.
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•Micro/nanostructured Zn films have been electrodeposited directly from ZnO precursor in deep eutectic solvent (DES).•The morphology of the Zn electrodeposits depends on the cathodic potential and temperature.•The electrodeposited Zn films exhibit homogeneous morphologies with controllable particle sizes and improved corrosion resistance.•Cu–Zn alloy films have also been electrodeposited directly from their metal oxides precursors in DES.
The electrodeposition of Zn and Cu–Zn alloy has been investigated in choline chloride (ChCl)/urea (1:2 molar ratio) based deep eutectic solvent (DES). Cyclic voltammetry study demonstrates that the reduction of Zn(II) to Zn is a diffusion-controlled quasi-reversible, one-step, two electrons transfer process. Chronoamperometric investigation indicates that the electrodeposition of Zn on a Cu electrode typically involves three-dimensional instantaneous nucleation with diffusion-controlled growth process. Micro/nanostructured Zn films can be obtained by controlling the electrodeposition potential and temperature. The electrodeposited Zn crystals preferentially orient parallel to the (101) plane. The Zn films electrodeposited under more positive potentials and low temperatures exhibit improved corrosion resistance in 3wt% NaCl solution. In addition, Cu–Zn alloy films have also been electrodeposited directly from CuO–ZnO precursors in ChCl/urea-based DES. The XRD analysis indicates that the phase composition of the electrodeposited Cu–Zn alloy depends on the electrodeposition potential.
Herein we report the demonstration of electrochemical deposition of silicon p–n junctions all in molten salt. The results show that a dense robust silicon thin film with embedded junction formation ...can be produced directly from inexpensive silicates/silicon oxide precursors by a two-step electrodeposition process. The fabricated silicon p–n junction exhibits clear diode rectification behavior and photovoltaic effects, indicating promise for application in low-cost silicon thin film solar cells.
The current Si production process is based on the high‐temperature (1700 °C) reduction of SiO2 with carbon that produces large amounts of CO2. We report an alternative low‐temperature (850 °C) ...process based on the reduction of SiO2 in molten CaCl2 that does not produce CO2. It utilizes an anode material (Ti4O7) capable of sustained oxygen evolution. Two types of this anode material, dense Ti4O7 and porous Ti4O7, were tested. The dense anode showed a better performance. The anode stability is attributed to the formation of a protective TiO2 layer on its surface. In situ periodic current reversal and ex situ H2 reduction could be used for extending the lifetime of the anodes. The findings show that this material can be applied as a recyclable anode in molten CaCl2. Si wires, films, and particles were deposited with this anode under different cathodic current densities. The prepared Si film exhibited ≈30–40 % of the photocurrent response of a commercial p‐type Si wafer, indicating potential use in photovoltaic cells.
Make a deposit: A highly electrically conductive anode, Ti4O7, was applied in molten CaCl2‐CaO‐SiO2 and successfully produced elementary Si without any CO2 emissions. In situ or ex situ methods can be used to efficiently regenerate the anode and extend its lifetime. The deposited Si films show good photoelectrochemical properties.
Ni/CaO, a low-cost dual-functional material (DFM), has been widely studied for integrated CO2 capture and hydrogenation. The core of this dual-functional material should possess both good CO2 ...capture–conversion performance and structural stability. Here, we synthesized Ni/CaO DFMs modified with alkali metals (Na, K, and Li) through a combination of precipitation and combustion methods. It was found that Na-modified Ni/CaO (Na-Ni/CaO) DFM offered stable CO2 capture–conversion activity over 20 cycles, with a high CO2 capture capacity of 10.8 mmol/g and a high CO2 conversion rate of 60.5% at the same temperature of 650 °C. The enhanced CO2 capture capacity was attributed to the improved surface basicity of Na-Ni/CaO. In addition, the incorporation of Na into DFMs had a favorable effect on the formation of double salts, which shorten the CO2 capture and release process and promoted DFM stability by hindering their aggregation and the sintering of DFMs.
The effect of carbon dioxide (CO2) on the desulfurization of sintering flue gas with hydrate (Ca(OH)2) as an absorbent was investigated, and the formation of calcium carbonate (CaCO3) and its effect ...on the desulfurization was discussed. The competitive relationship between carbon dioxide (CO2) and sulfur dioxide (SO2) with the deacidification agent in sintering flue gas is discussed thermodynamically, showing that sulfates are more likely to be generated under high oxygen potential conditions and that SO2 reacts more preferentially than CO2 under a thermodynamic standard state. The amount of produced CaCO3 increases under the condition that the CO2 concentration is absolutely dominant to SO2 in the sintering flue gas atmosphere. The effect of temperature, humidity and CO2 concentration on the desulfurization of Ca(OH)2 are discussed experimentally. The increasing temperature is not conducive to desulfurization, and the humidity can promote desulfurization, while excessive humidity could inhibit desulfurization. The suitable relative humidity is 20%. In situ generated calcium carbonate has a certain desulfurization effect, but the desulfurization effect is not as good as Ca(OH)2. However, a large proportion of CaCO3 was produced in the desulfurization ash under the condition that CO2 concentration was absolutely dominant to SO2 in the sintering flue gas atmosphere.
The effects of the application of iron coke in hydrogen-rich blast furnace atmosphere on the softening and melting performance of burden were studied.The results indicated that with the increase in ...hydrogen content, the cohesive zone of mixed burden became narrower and the permeability of charge was improved, and the suitable hydrogen content was 10vol.-%. The application of iron coke could promote the iron ore reduction and carburizing of iron, decrease the melting temperature by 1-10°C, decrease the dripping temperature by 5-16°C, narrow the cohesive zone, improve the air permeability with S value decrease of 3.19-13.87 kPa °C, and reduce the dissolution loss of coke and ensure the skeleton function of coke. The suitable burden structure was confirmed as follows, i.e. the ratio of pellets and sinter is 4:6, and the ratio of iron coke and coke is 2:8.
The low-cost production of high-purity metallic iron is of great practical importance. Herein, we report the direct production of high-purity metallic iron (99.92%) via a one-step electrochemical ...strategy in molten CaCl2–CaO–Fe2O3 system at 850°C. The involved CaO-assisted dissolution of Fe2O3 and electrodeposition mechanism were systematically studied, and the obtained iron products were characterized using scanning electron microscopy, inductively-coupled high-frequency plasma emission spectrometry, and glow discharge mass spectrometry. The results show that the crystalline iron products with tunable morphologies can be obtained in a controlled manner. The electrolysis parameters (voltage, current density, electrodeposition time and substrate material) have significant effects on the electrodeposition process and the characteristics of iron products. In particular, high-purity dense iron film can be directly electrodeposited at 15 mA∙cm−2, and its thickness increases considerably with increasing electrodeposition time. Furthermore, the as-deposited iron product can also be processed into bulk iron materials with high-purity of 99.995 wt.% by plasma melting for the potential applications. In general, this one-step electrodeposition process provides an acid-/alkaline-free strategy for the facile production of high-purity iron materials direct from Fe2O3.
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