1,721,140 research outputs found
Silicon-based photovoltaic solar cells
No full textAn overview is given of materials and manufacturing issues throughout the supply chain of the solar silicon photovoltaic industry. The historical evolution of the industry and future projections are discussed. A brief review is then given of each step of the industry supply chain: polysilicon production, crystallisation and wafering, and the design and manufacturing of crystalline silicon solar cells. The chapter concludes with a discussion of emerging and future advances that will enable scaling of the industry to the terawatt level
Ion pairing effects on substitutional impurity diffusion in silicon
No full textRecent experiments have shown that ion pairing has a major influence on the diffusion and precipitation of oppositely charged impurities in silicon. Published data are used to obtain ion pairing coefficients Ω for n‐type impurities with B and In. A single value, Ω=0.17/ni, suffices to describe the cases P‐B, As‐B, and Sb‐B. For P‐In and Sb‐In, Ω is roughly an order of magnitude smaller. These observations are consistent with the picture that paired ions occupy adjacent substitutional sites, with a small perturbation in their Coulomb binding arising from elastic effects
The scientific case for a climate \u27war effort\u27
Full text linkThis year has seen major developments in climate science that are crucially important for green business. Scientists have learned that global warming is accelerating with a substantial likelihood that it will reach the crucial 1.5C above the pre-industrial baseline temperature at some time between 2025 and 2030. The implications for people and businesses are dramatic and call for evidence-based policy decisions of breath-taking scope within the very near future. As of today, one thing is clear: the world will change dramatically as a result of destructive climate and weather events during the next decade, likely social unrest, and the choices governments will have to make to survive these events
Diffusion in a single crystal within a stressed environment
No full textThe energetics of point defects and diffusion in a single crystal is analyzed with respect to stress in overlying or encapsulating layers. The resulting theory subsumes previous formulations of pressure and stress effects on diffusion. A key prediction is that stress on the overlayer side of the crystal boundary perturbs point defect concentrations in the underlying crystal. The effect can occur without significant strain in the crystal itself. The theory is compared with available published data on diffusion in silicon under thin strained overlayers. \ua9 2007 The American Physical Society
Current rapid global temperature rise linked to falling SO<sub>2</sub> emissions
Full text linkIt is widely held that global temperature variations on time scales of a decade or less are primarily caused by internal climate variability, with smaller contributions from changes in external climate forcing such as solar irradiance. This paper shows that observed variations in global mean surface temperature, TGS , and ocean heat content (OHC) during the last 1–2 decades imply major changes in climate forcing during this period. In a first step, two independent methods are used to evaluate global temperature corrected for ocean–atmosphere heat exchange. El Ni\uf1o/Southern Oscillation (ENSO) corrected TGS (written as T\u27GS ) is shown to agree closely with a novel temperature metric θ that combines uncorrected TGS with scaled OHC. This agreement rules out a substantial 21st-century contribution to TGS from ocean-atmosphere heat exchange. In contrast to TGS , the time series T\u27GS(t) provides a clear fingerprint of transient global cooling associated with major volcanic eruptions, enabling a more accurate empirical estimate of the climate response of the global mean surface. This allows more accurate estimation of the net climate forcing by stratospheric aerosols and solar irradiance, which is then subtracted from T\u27GS(t) to determine the underlying signal of anthropogenic global warming. Key features of this signal are a slowdown from the late 1990s to 2011 – corresponding to the well known climate hiatus – and a subsequent sharp upturn indicating a steep increase in anthropogenic climate forcing. It is argued that the only plausible cause for this increase is a large fractional decrease in tropospheric aerosol cooling. This attribution is supported by satellite-based observations of a >50 % decrease in SO2 emissions from large sources during the last six years. It suggests that current clean-air policies and replacement of coal by natural gas are driving a significant human made climatic event, 2–4 times faster than greenhouse driven warming alone. If confirmed, this implies a considerably shortened timescale to meet the IPCC 1.5\ub0C objective, with major implications for near-term carbon emission policies.o</sub
Anthropogenic Climate Change in the Zero-Carbon Era
No full textGlobal warming is a result of \u27temperature forcing\u27, the net imbalance between energy fluxes entering and leaving the climate system and arising within it. At present humanity introduces temperature forcing through greenhouse gas emissions, agriculture, and thermal emissions from fuel burning. Up to now climate projections, based on projected GHG emissions and neglecting thermal emissions, typically foresee maximum forcing at a date occurring from midcentury onwards, followed by a slow decline due to elimination of carbon emissions. However, under reasonable scenarios of growth in primary energy use, even if we switch completely to generation by zero-carbon fuel burning (nuclear or fossil with carbon capture) temperature forcing will be sustained and even increase through the second half of the century as a result of the additional heat injected into the climate system. A potential solution to this problem is to develop energy generation technologies that remove heat from the climate system, or as a temporary solution \u27dump\u27 heat in the deep ocean. Two such technologies, both relying on solar energy, are discussed in this paper
Doping characterization for germanium-based microelectronics and photovoltaics using the differential Hall technique
No full textIn this coming decade, complementary metal-oxide-semiconductor microelectronic devices may undergo a major change with the implementation of germanium channels. Likewise, the performance of photovoltaic cells based on elemental semiconductors will continue to be optimized. Both technologies will rely on a detailed and thorough understanding of electrical properties, and here, precise doping characterization will play a key role. The differential Hall technique combines resistivity and Hall-effect measurements with successive surface layer removal, allowing one to measure independent carrier concentration and mobility depth profiles. In this Letter, we apply the technique for both microelectronic- and photovoltaic-relevant doping structures in germanium. Controllable and uniform layer removal is achieved with tailored depth resolution (<1-20 nm) for a range of doping structures (30-600 nm). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705293
TCAD in the semiconductor industry and its advantages for solar cell manufacturing
No full textTechnology computer-aided design (TCAD) is pervasive throughout research, development and manufacturing in the semiconductor industry. It allows very low-cost evaluation of process options and competing technologies, guides process development and transfer to production and supports more efficient process improvement with minimal down time in the factory environment. This paper reviews the use of TCAD in the semiconductor industry and shows, with some illustrative examples, its important enabling role for the PV industry
Thermal emissions and climate change: Cooler options for future energy technology
No full textGlobal warming is a consequence of ‘temperature forcing’, a net imbalance between energy fluxes entering and leaving the global climate system and energy generation within this system. Humanity introduces positive forcings through greenhouse gas (GHG) emissions, agriculture, and increasingly thermal emissions - heat released as a result of energy generation and use. Up to now, climate change projections have neglected thermal emissions, and typically assume a peak in forcing due to GHG emissions around the middle of this century [1,2]. Here we show that, if humanity’s future energy use grows at just 1% per year, slower than in recent history, and if thermal emissions are not controlled through changes in technology, the total forcing due to all emissions will not peak and decline significantly as currently predicted, but after a slight dip will continue to rise. This problem can be combated by geoengineering and mitigated by renewable energy sources that minimize waste heat. Such approaches could be combined in reflective wide-bandgap photovoltaic technology, which offers the possibility of a strong negative temperature forcing together with electrical power generation
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