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International audienceCu2ZnSnSe4 solar cell absorbers are synthesized by large-area electrodeposition of metal stack precursors followed by selenization. A champion solar cell exhibits 8.2% power conversion efficiency, a new record for Cu2ZnSnSe4 solar cells prepared from electrodeposited metallic precursors. Significant improvements of device performance are achieved by the application of two etching procedures and buffer layer optimization. These results validate electrodeposition as a credible alternative to vacuum processes (sputtering, co-evaporation) for earth-abundant thin-film solar cell fabrication at low cost. Copyright (C) 2015 John Wiley & Sons, Ltd

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Bipolar membrane electrodialysis is used in three compartment configuration to regenerate formic acid and sodium hydroxide from sodium formate. The preceding study [7] showed that diffusion of molecular formic acid is responsible of the loss of acid current efficiency. The present study shows the following results: the diffusion of molecular formic acid through the bipolar membrane explains quantitatively the presence of sodium formate in the sodium hydroxide solution. The loss of acid current efficiency is due to diffusion of molecular acid through both anion exchange and bipolar membranes. The sodium hydroxide current efficiency is determined by acid diffusion through the bipolar membrane and OHleakage through the cation exchange membrane. The flux of acid diffusion in the membranes is proportional to acid concentration. The transfer coefficients vary with the temperature. A model based on mass balance is proposed to describe the electrodialysis. Some experimental parameters like volume variations are needed. It is seen that, following the model, a low temperature is favourable to the process. So does an increase of current density. The nature of anion exchange membrane also affects diffusion. It is found that PC acid 100 membrane is the less permeable to formic acid among 5 tested membranes. The flux of hydroxide ion through the CMB cation exchange membrane is evaluated.

Salinity gradient power is a renewable, non-intermittent, and neutral carbon energy source. Reverse electrodialysis is one of the most efficient and mature techniques that can harvest this energy from natural estuaries produced by the mixture of seawater and river water. For this, the development of cheap and suitable ion-exchange membranes is crucial for a harvest profitability energy from salinity gradients. In this work, both anion-exchange membrane and cation-exchange membrane based on poly(epichlorohydrin) and polyvinyl chloride, respectively, were synthesized at a laboratory scale (255 cm2) by way of a solvent evaporation technique. Anion-exchange membrane was surface modified with poly(ethylenimine) and glutaraldehyde, while cellulose acetate was used for the cation exchange membrane structural modification. Modified cation-exchange membrane showed an increase in surface hydrophilicity, ion transportation and permselectivity. Structural modification on the cation-exchange membrane was evidenced by scanning electron microscopy. For the modified anion exchange membrane, a decrease in swelling degree and an increase in both the ion exchange capacity and the fixed charge density suggests an improved performance over the unmodified membrane. Finally, the results obtained in both modified membranes suggest that an enhanced performance in blue energy generation can be expected from these membranes using the reverse electrodialysis technique.

This work reports the Raman scattering characterisation of CuInSe2 precursors grown by single step electrodeposition and the corresponding layers recrystallised under sulphurising conditions for solar cell devices. The analysis of the spectra measured on the as‐grown precursors has allowed identifying the main secondary phases in these layers with elemental Se, Cu–Se phases and chalcopyrite Cu‐poor ordered vacancy domains. To deepen in the identification of the Cu–Se phases, these measurements have been correlated with the analysis of binary Cu–Se layers. The experimental data indicate that formation of both Se and Cu–Se phases is likely controlled by the Se content in the layers. For values of stoichiometry below 1.15, excess Cu in the layers is accommodated in a phase with very low Raman efficiency (as Cu2Se). Increasing the content of Se leads to an increase in the spectral contribution from both Se and Cu2–x Se, being the formation of these phases likely favoured under high excess Se conditions. The characterisation of the corresponding recrystallised layers has allowed analysing the impact of the presence of the secondary phases in the as‐grown absorbers on the performance of the final solar cells. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)