The History of Photovoltaics with Emphasis on CdTe Solar Cells and Modules

Among thin-film photovoltaic technology, cadmium telluride (CdTe) has achieved a truly impressive development that can commercially compete with silicon, which is still the king of the market. Solar cells made on a laboratory scale have reached efficiencies close to 22%, while modules made with fully automated in-line machines show efficiencies above 18%. This success represents the result of over 40 years of research, which led to effective and consolidated production processes. Based on a large literature survey on photovoltaics and on the results of research developed in our laboratories, we present the fabrication processes of both CdTe polycrystalline thin-film solar cells and photovoltaic modules. The most common substrates, the constituent layers, their interaction, the interfaces and the different “tricks” necessary to obtain highly efficient devices will be analyzed. A realistic industrial production process will be analytically described. Moreover, environmental aspects, end-of-life recycling and the life cycle assessment of CdTe-based modules will be deepened and discussed

Polycrystalline Cu(InGa)Se2/CdS Thin Film Solar Cells Made by New Precursors

In the last five years photovoltaic modules production continued to be one of the rapidly growing industrial sectors, with an increase well in excess of 40% per year. This growth is driven not only by the progress in materials and technology, but also by incentives to sup\u2010 port the market in an increasing number of countries all over the world. Besides, the in\u2010 crease in the price of fossil fuels in 2008, highlighted the necessity to diversify provisioning for the sake of energy security and to emphasize the benefits of local renewable energy sour\u2010 ces such as solar energy. The high growth was achieved by an increase in production capaci\u2010 ty based on the technology of crystalline silicon, but in recent years, despite the already very high industrial growth rates, thin film photovoltaics has grown at an increasingly fast pace and its market share has increased from 6% in 2006 to over 12% in 2010. However, the ma\u2010 jority of photovoltaic modules installed today are produced by the well-established technol\u2010 ogy of monocrystalline and polycrystalline silicon, which is very close to the technology used for the creation of electronic chips. The high temperatures involved, the necessity to work in ultra-high vacuum and the complex cutting and assembly of silicon "wafers", make the technology inherently complicated and expensive. In spite of everything, silicon is still dominating the photovoltaic market with 90% of sales. Other photovoltaic devices based on silicon are produced in the form of "thin films" or in silicon ribbons; these devices are still in the experimental stage

Silane-Mediated Expansion of Domains in Si-Doped κ-Ga2O3 Epitaxy and its Impact on the In-Plane Electronic Conduction

Unintentionally doped (001)-oriented orthorhombic κ-Ga2O3 epitaxial films on c-plane sapphire substrates are characterized by the presence of ≈ 10 nm wide columnar rotational domains that can severely inhibit in-plane electronic conduction. Comparing the in- and out-of-plane resistance on well-defined sample geometries, it is experimentally proved that the in-plane resistivity is at least ten times higher than the out-of-plane one. The introduction of silane during metal-organic vapor phase epitaxial growth not only allows for n-type Si extrinsic doping, but also results in the increase of more than one order of magnitude in the domain size (up to ≈ 300 nm) and mobility (highest µ ≈ 10 cm2V−1s−1, with corresponding lowest ρ ≈ 0.2 Ωcm). To qualitatively compare the mean domain dimension in κ-Ga2O3 epitaxial films, non-destructive experimental procedures are provided based on X-ray diffraction and Raman spectroscopy. The results of this study pave the way to significantly improved in-plane conduction in κ-Ga2O3 and its possible breakthrough in new generation electronics. The set of cross-linked experimental techniques and corresponding interpretation here proposed can apply to a wide range of material systems that suffer/benefit from domain-related functional properties

Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry

Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase

The History of Photovoltaics with Emphasis on CdTe Solar Cells and Modules

Among thin-film photovoltaic technology, cadmium telluride (CdTe) has achieved a truly impressive development that can commercially compete with silicon, which is still the king of the market. Solar cells made on a laboratory scale have reached efficiencies close to 22%, while modules made with fully automated in-line machines show efficiencies above 18%. This success represents the result of over 40 years of research, which led to effective and consolidated production processes. Based on a large literature survey on photovoltaics and on the results of research developed in our laboratories, we present the fabrication processes of both CdTe polycrystalline thin-film solar cells and photovoltaic modules. The most common substrates, the constituent layers, their interaction, the interfaces and the different “tricks” necessary to obtain highly efficient devices will be analyzed. A realistic industrial production process will be analytically described. Moreover, environmental aspects, end-of-life recycling and the life cycle assessment of CdTe-based modules will be deepened and discussed

CdTe-Based Photodetectors and Solar Cells

In this chapter we will show how much appreciated were the electro-optical characteristics of one of the most widely used semiconductors of the II-VI family, Cadmium Telluride or CdTe. High quality single crystals with industrially appreciable dimensions have been easily obtained since the beginning of the CdTe epopee. Exploiting its very high transparency in the mid-infrared it was firstly employed as window for i.r. laser applications. Its role, as a material for developing electro-optical modulators needed for the evolution of power CO2-based lasers, was crucial. In more modern times, with the advent of nanotechnologies, CdTe has found considerable success as a UV-Vis photodetector if used in the form of dots, ribbons, belts and, more in general, when it is possible to exploit quantum confinement in reduced dimensions. But where CdTe has been most successful is in the photovoltaic field, where solar cells and photovoltaic modules, with conversion efficiency greater than 22% and 19% respectively, have been made. To date, among thin-film technologies, CdTe-based modules occupy the first place on the market and more than 8% globally. We will talk about this and much more in the rest of this chapter by going into the detail of the photodetectors and, mainly, of the solar cells, revealing the smartest tricks normally used to make these devices sustainable, efficient and cost-effective

Photovoltaics with Emphasis on CdTe Solar Cells and Modules

A brief overview of the main photovoltaic technologies is chronologically presented. Single-crystal and multi-crystalline, epitaxial and thin film inorganic materials are widely used as absorbers in high efficiency solar cells and modules. A schematic representation of the principal devices developed in more then 70 years of research will be displayed and commented. Among thin-film technology, cadmium telluride (CdTe) has achieved a truly impressive development that can commercially compete with silicon, which is still the king of the market. Solar cells made on a laboratory scale have reached efficiencies close to 22%, while modules made with fully automated in-line machines show efficiencies above 18%. Based on the research developed in our laboratory, the fabrication processes of both CdTe polycrystalline thin-film solar cells and photovoltaic modules are critically discussed. The most common substrates, the constituent layers and their interaction, the interfaces and the different &amp;ldquo;tricks&amp;rdquo; commonly used for obtaining highly efficient devices will be analyzed. A realistic industrial production process will be analytically described.</jats:p