Open Source 3-D Printers: An Appropriate Technology for Developing Communities

International audienceThe recent introduction of RepRap (Self-Replicating Rapid Prototyper) 3-D printers and the resultant open source technological improvements have resulted in affordable 3-D printing, enabling low-cost distributed manufacturing for individuals. This development and others such as the rise of open source-appropriate technology (OSAT) and solar powered 3-D printing are moving 3-D printing from an industry specific technology to one that could be used in the developing world for sustainable development. In this paper, we explore some specific technological improvements and how distributed manufacturing with open-source 3-D printing can provide sustainable development by creating wealth for developing world communities through the ability to print less expensive and customized products. Conclusions on the technical viability of 3-D printing to assist in development and recommendations on how developing communities can fully exploit this technology have been outlined

Advances in Plasmonic Light Trapping in Thin-Film Solar Photovoltaic Devices

This chapter reviews the recent promising advances in the use of plasmonic nanostructures forming metamaterials to improve absorption of light in thin-fi lm solar photovoltaic (PV) devices. Sophisticated light management in thin-fi lm PV has become increasingly important to ensure absorption of the entire solar spectrum while reducing semiconductor absorber layer thicknesses, which reduces deposition time, material use, embodied energy, greenhouse gas emissions, and economic costs. Metal nanostructures have a strong interaction with light, which enables unprecedented control over the propagation and the trapping of light in the absorber layer of thin-fi lm PV. The literature is reviewed for both theoretical and experimental work on multiple nanoscale geometries of both plasmonic absorbers and PV materials. Finally, the use of nanostructures to improve light trapping in PV is outlined to guide development

Design of multijunction photovoltaic cells optimized for varied atmospheric conditions

Band gap engineering provides an opportunity to not only provide higher overall conversion efficiencies of the reference AM1.5 spectra but also customize PV device design for specific geographic locations and microenvironments based on atmospheric conditions characteristic to that particular location. Indium gallium nitride and other PV materials offer the opportunity for limited bandgap engineering to match spectra. The effects of atmospheric conditions such as aerosols, cloud cover, water vapor, and air mass have been shown to cause variations in spectral radiance that alters PV system performance due to both overrating and underrating. Designing PV devices optimized for spectral radiance of a particular region can result in improved PV system performance. This paper presents a new method for designing geographically optimized PV cells with using a numerical model for bandgap optimization. The geographic microclimate spectrally resolved solar flux for twelve representative atmospheric conditions for the incident radiation angle (zenith angle) of 48.1° and fixed array angle of 40° is used to iteratively optimize the band gap for tandem, triple, and quad-layer of InGaN-based multijunction cells. The results of this method are illustrated for the case study of solar farms in the New York region and discussed

Review of near-field optics and superlenses for sub-diffraction-limited nano-imaging

Near-field optics and superlenses for imaging beyond Abbe’s diffraction limit are reviewed. A comprehensive and contemporary background is given on scanning near-field microscopy and superlensing. Attention is brought to recent research leveraging scanning near-field optical microscopy with superlenses for new nano-imaging capabilities. Future research directions are explored for realizing the goal of low-cost and high-performance sub-diffraction-limited imaging systems

Limitations of ultra-thin transparent conducting oxides for integration into plasmonic-enhanced thin-film solar photovoltaic devices

This study investigates ultra-thin transparent conducting oxides (TCO) of indium tin oxide (ITO), aluminum-doped zinc oxide (AZO) and zinc oxide (ZnO) to determine their viability as candidate materials for use in plasmonic-enhanced thin-film amorphous silicon solar photovoltaic (PV) devices. First a sensitivity analysis of the optical absorption for the intrinsic layer of a nano-disk patterned thin-film amorphous silicon-based solar cell as a function of TCO thickness (10-50 nm) was performed by simulation. These simulation results were then used to guide the design of the experimental work which investigated both optical and electrical properties of ultra-thin (10 nm on average) films simultaneously deposited on both glass and silicon substrates using conventional rf sputtering. The effects of deposition and post-processing parameters on material properties of ITO, AZO and ZnO ultra-thin TCOs were probed and the suitability of TCOs for integration into plasmonic-enhanced thin-film solar PV devices was assessed. The results show that ultra-thin TCOs present a number of challenges for use as thin top contacts on plasmonic-enhanced PV devices: (1) optical and electrical parameters differ greatly from those of thicker (bulk) films deposited under the same conditions, (2) the films are delicate due to their thickness, requiring very long annealing times to prevent cracking, and (3) reactive gases require careful monitoring to maintain stoichiometry. The results presented here found a trade-off between conductivity and transparency of the deposited films. Although the sub 50 nm TCO films investigated exhibited desirable optical properties (transmittance greater than 80 %), their resistivity was too high to be considered as materials for the top contact of conventional PV devices. Future work is necessary to improve thin TCO properties, or alternative materials, and geometries are needed in plasmonic-based amorphous silicon solar cells. The stability of ultra-thin TCO films also needs to be experimentally investigated under normal device operating conditions