Impact of selenization with NaCl treatment on the physical properties and solar cell performance of crack-free Cu(In,Ga)Se2 microcrystal absorbers.

In this study, we developed an ink using hexanethiol and Cu(In,Ga)Se2 microcrystals (CIGSe MCs) to make thin films via doctor blade coating. Besides, crack-free thin films were obtained by optimizing CIGSe MC powder concentration and annealing temperature. Subsequently, single-step selenization was performed with and without sodium chloride (NaCl) surface treatment by carefully tuning the temperature. A crack-free surface with densely packed grains was obtained at 500 °C after NaCl treatment. Moreover, the structural parameters of the thin film (annealed at 350 °C) were significantly modified via selenization with NaCl at 500 °C. For instance, the FWHM of the prominent (112) plane reduced from 1.44° to 0.47°, the dislocation density minimized from 13.10 to 1.40 × 1015 lines per m2, and the microstrain decreased from 4.14 to 1.35 × 10-3. Remarkably, these thin films exhibited a high mobility of 26.7 cm2 V-1 s-1 and a low resistivity of 0.03 Ω cm. As a proof of concept, solar cells were engineered with a device structure of SLG/Mo/CIGSe/CdS/i-ZnO/Al-ZnO/Ag, wherein a power conversion efficiency (PCE) of 5.74% was achieved with exceptional reproducibility. Consequently, the outcomes of this investigation revealed the impact of selenization temperature and NaCl treatment on the physical properties and PCE of hexanethiol-based crack-free CIGSe MC ink-coated absorbers, providing new insights into the groundwork of cost-effective solar cells.

The visible-light-driven photocatalytic reduction of Cr6+ using BiVO4: assessing the effect of Au deposition and the reaction parameters.

In this work, fern-leaf-like BiVO4 was used to photocatalytically reduce Cr6+ in water. Nanosized BiVO4 displayed bandgap energy and specific surface area of 2.49 eV and 5.65 m2 g-1, respectively. Metallic Au nanoparticles were deposited on the BiVO4 to increase the photocatalytic performance. To optimize the reaction conditions, the sacrificial agents methanol, ethanol, formic acid, dimethyl sulfoxide, and KI were tested, while different catalyst dosages and Au loadings were assessed. The best sacrificial agent was formic acid, which was used at an optimal concentration of 0.01 mol L-1. The complete removal of Cr6+ was attained after 90 min of visible light irradiation using a catalyst dosage of 1.5 g L-1. Depositing metallic Au nanoparticles barely improved the photocatalytic performance, thus unmodified BiVO4 was used to remove Cr6+ in tap water. The matrix effect slowed the photocatalytic process, and the complete removal of Cr6+ was achieved in 120 min. Cr3+ and Cr6+ species were precipitated on the catalyst surface at the end of the photocatalytic process; still, BiVO4 displayed high stability after three reaction cycles.