High-Efficiency Silicon Solar Cells—Materials and Devices Physics

High-efficiency Si solar cells have attracted great attention from researchers, scientists, engineers of photovoltaic (PV) industry for the past few decades. Many researchers, scientists, and engineers in both academia and industry seek solutions to improve the cell efficiency and reduce the cost. This desire has drawn stronger support from major funding agencies and industry and stimulated a growing number of major research and research infrastructure programs, and a rapidly increasing number of publications in this filed. This article reviews materials, devices, and physics of high-efficiency Si solar cells developed over the last 20 years and presents representative examples of superior performances and competitive advantages. In this paper there is a fair number of topics, not only from the material viewpoint, introducing various materials that are required for high-efficiency Si solar cells, such as base materials (FZ-Si, CZ-Si, MCZ-Si, and multi-Si), emitter materials (diffused emitter and deposited emitter), passivation materials (Al-BSF, high-low junction, SiO₂, SiO_x, SiN_x, Al₂O₃ and a-Si:H), and other functional materials (antireflective layer, transparent conductive oxide and metal electrode), but also from the device and physics point of view, elaborating on physics, cell concept, development, and status of most types of high-efficiency Si solar cells, including passivated emitter and rear contact (PERC), passivated emitter and rear locally diffused (PERL), passivated emitter and rear totally-diffused (PERT), Pluto, PANDA, interdigitated back-contacted (IBC), emitter-wrap-through (EWT), metallization-wrap-through (MWT), heterojunction with intrinsic thin-layer (HIT), and so on. Finally, the technical data of these high-efficiency Si solar cells has been tabulated.     

The effect of Zn on precipitation in Al–Mg–Si alloys

Effects of addition of Zn (up to 1 wt%) on microstructure, precipitate structure and intergranular corrosion (IGC) in an Al–Mg–Si alloys were investigated. During ageing at 185?°C, the alloys showed modest increases in hardness as function of Zn content, corresponding to increased number densities of needle-shaped precipitates in the Al–Mg–Si alloy system. No precipitates of the Al–Zn–Mg alloy system were found. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), the Zn atoms were incorporated in the precipitate structures at different atomic sites with various atomic column occupancies. Zn atoms segregated along grain boundaries, forming continuous film. It correlates to high IGC susceptibility when Zn concentration is ~1wt% and the materials in peak-aged condition.