Fabricating energy devices with low environmental impacts

Abstract

Techniques such as electrochemical atomic layer epitaxial deposition can be used to grow high-quality pseudo-2D layers of photovoltaic materials.Efforts to reduce the rate of carbon emissions from industry, 1 as well as the impending economic and social problems that could arise from the depletion of fossil fuels, 2 are the two driving forces for the development of devices that can generate electric power from renewable sources. It is necessary for research and development in this field to satisfy a few major requirements. In the last few decades, the increasing demand for high-tech applications has led to increasing solicitation of mineral deposits and has brought many rare metals to the brink of irreversible depletion. 3 It is therefore necessary for new devices to be based on abundant materials that are available on a global or local scale. The whole 'life cycle' of the materials must also be environmentally friendly (i.e., the materials must be non-toxic and easily recycled). Moreover, the materials must be energetically favorable, i.e., they must involve low-energy consumption processes during all the phases of the life cycle (production, to maintenance, to decommission, to recycling). This final aspect-which can be determined accurately through a full life cycle assessment (LCA)-depends on the energy costs and energy conversion efficiency of the device itself. In a full LCA, several parameters are estimated. These include the payback time (time required to earn the energy costs of the production process), the energy return on energy investment (ratio between the energy produced by and the energy costs of the system along the whole life cycle), 4 and the net energy (the energy delivered to society for discretionary uses after all the energetic costs are subtracted from the energy produced). This last figure of merit (i.e., the net energy) is a crucial parameter for defining energy policy. 4 All these requirements for renewable energy devices can be met satisfactorily by solar cells that are based on pseudo-ternary sulfides, such as stannite (Cu 2 FeSnS 4 ), kuramite (Cu 3 SnS 4 ), and kesterite (Cu 2 ZnSnS 4 ). 5 Kesterite-type semiconductors are Figure 1. Schematic illustration of the electrochemical atomic layer epitaxial deposition (ECALE) technique for the growth of quaternary metallic compound thin films.generally synthesized by high-temperature solidification, in the vapor phase, or under high-vacuum conditions. Other easier and cheaper methods (e.g., from aqueous solutions), however, can also be considered. Electrochemical techniques, for example, are particularly suitable for satisfying the requirements. Indeed, with these methods, a low cost can be achieved with relatively simple instrumentation, low working temperatures, and accurate control of the experimental parameters. 6 Furthermore, morphological, structural, and compositional control of the final deposited film can be obtained.In our work, we use a particular electrochemical techniqueknown as electrochemical atomic layer epitaxial deposition...

Thermochemistry of the E-ALD process for the growth of CuxZnyS on Ag(111): Interpretation of experimental data

“…Among them, Cu 2+ (aq) act as master species, while the others are defined as secondary species by means of formation reactions from the master species (e.g. Cu 2+ + 2OH -= Cu(OH) 2 Debye-Huckel activity model) 36 .…”

Green and scalable synthesis of nanocrystalline kuramite

“…Most of these processes yield nanocrystalline materials that can be easily dispersed in inks [28–33], leading to a plethora of new applications, even processing on flexible surfaces. Most of the efforts in this research field aim at the optimal trade-off between the solar energy conversion performance, scalability and sustainability of these nanocrystalline multinary sulfides [34–35]. To this end, researchers have produced many different polymorphic and isomorphic phases related to kuramite.…”

Electrodeposition and Characterization of p and n Sulfide Semiconductors Composite Thin Film

“…In fact, they allow to work with diluted aqueous solutions, at atmospheric pressure and at temperatures lower than 100 • C. Electrodeposition allows the synthesis of nanomaterials with a high degree of structural and compositional control. [10][11][12] Among electrodeposition techniques, one that best fits these key aims is Electrochemical Atomic Layer Deposition (E-ALD), 13,14 which is also called ECALE (Electrochemical Atomic Layer Epitaxy) when the growth can be considered epitaxial. E-ALD is a layer by layer technique, which exploits surface limited reactions (SLR), as Under Potential Deposition (UPD) phenomena, allowing the growth of a compound simply alternating the various SLR of the elements.…”

“…E-ALD is a layer by layer technique, which exploits surface limited reactions (SLR), as Under Potential Deposition (UPD) phenomena, allowing the growth of a compound simply alternating the various SLR of the elements. E-ALD has been used to grow many binary and ternary compounds, [12][13][14][15] and particularly in the last years, to prepare p semiconductors belonging to the Cu-Zn-S system. [16][17][18][19] In this work we aimed to test and verify the technical feasibility of growing, under laboratory conditions, a complete p-n junction through E-ALD.…”