Modelling solar cells has, in recent years, become a fundamental tool for their optimum design. Here, we present an optical study of CuInGaSe ₂ (CIGS) solar cells in order to improve them by selecting the appropriate transparent conductive oxide (TCO) layer thickness. The system of interest in our case was glass/TCO/CdS/CIGS/Mo, considering radiation incident perpendicular to the cell from the glass and taking into account the absorbent nature of the TCO, CdS and CIGS layers. The reflectance of this layered system was calculated using the optical matrix method considering the three absorbent layers and the reflectance at the Mo substrate. In addition, the transmittance of the TCO layer was also calculated. Then, having the constant thickness of the CIGS (1 μ m) and CdS (0.1 μ m) layers, the weighted average of the cell reflectance and the TCO transmittance in the AM1.5 solar spectrum were calculated for different TCO thickness in the range from 0.1 to 1 μ m. Finally, we defined a figure of merit that involves the total cell reflectance, the transmittance and the sheet resistivity of the TCO as a function of the TCO layer thickness. Our results indicate that the ZnO film thickness can be increased to 1 μ m with a possible improvement of the cell performance compared to cells with typical TCO thickness around 500 nm.

Recycled concrete aggregates (RCAs) have been demonstrated as an alternative source to exhaustible natural aggregates. In this paper, we focus on the enhancement treatments for coarse and fine RCAs and the effect of these treatments on the durability of recycled concrete (RC) made from treated RCAs by the weakening and strengthening of the cement paste adhered to their surface. We conducted comparative analyses on the improvement of durability and mechanical properties. The results showed that the reduction of water absorption in RCAs increases the compressive strength of RC and that there is a strong linear trend of improvement in the carbonation depth, chloride ion penetration, and compressive strength of RC. For fine and coarse RCAs, the treatment mechanism and particle size are determinants in efficiently improving RC durability.

Copper-based composite materials are widely applied in the field of electronics and electrical engineering as highly conductive materials for operation at high temperatures. In this study, copper-based composites were produced by the powder metallurgy and reinforced with 1.0, 1.5, 2.0, 2.5, and 3.0% vol alumina nanometer sized particles. Powders were mixed by glass ball milling for 6 h at 100 rpm. Samples were compacted at 420 MPa in a steel die and sintered at 900°C for 15 min in an argon chamber. Scanning electron microscopy, X-ray diffraction, Vickers micro-hardness, and tensile tests were performed to analyze the influence of the alumina content on the mechanical, structural, and micro-structural properties of the copper-alumina composites that were manufactured by three steps of the powder metallurgy technique. X-ray diffraction patterns showed that during the ball milling, cold compacting, and sintered steps no new crystalline phases were formed. Scanning electron microscopy images providing information related to the alumina layering that restricted the reinforcement mechanism and the expected improvement in the composite mechanical properties.