On top of commercial photovoltaics

The efficiency of single junction solar cells is intrinsically limited and high efficiency multi junctions are not cost effective yet. Now, semi transparent perovskite solar cells suggest that low cost multi junctions could be within reac

Proposal for the observation of nonlocal multipair production: the biSQUID

We propose an all-superconducting three-terminal setup consisting in a carbon nanotube (or semiconducting nanowire) contacted to three superconducting leads. The resulting device, referred to as a "biSQUID", is made of four quantum dots arranged in two loops of different surface area. We show how this biSQUID can prove a useful tool to probe nonlocal quantum phenomena in an interferometry setup. We study the measured critical current as a function of the applied magnetic field, which shows peaks in its Fourier spectrum, providing clear signatures of multipair Josephson processes. The device does not require any specific fine-tuning as these features are observed for a wide range of microscopic parameters -- albeit with a non-trivial dependence. Competing effects which may play a significant role in actual experimental realizations are also explored.Comment: 13 pages, 9 figure

Multipair DC-Josephson Resonances in a biased all-superconducting Bijunction

An all-superconducting bijunction consists of a central superconductor contacted to two lateral superconductors, such that non-local crossed Andreev reflection is operating. Then new correlated transport channels for the Cooper pairs appear in addition to those of separated conventional Joseph- son junctions. We study this system in a configuration where the superconductors are connected through gate-controllable quantum dots. Multipair phase-coherent resonances and phase-dependent multiple Andreev reflections are both obtained when the voltages of the lateral superconductors are commensurate, and they add to the usual local dissipative transport due to quasiparticles. The two-pair resonance (quartets) as well as some other higher order multipair resonances are {\pi}-shifted at low voltage. Dot control can be used to dramatically enhance the multipair current when the voltages are resonant with the dot levels.Comment: 6 page

Oxygen vacancies in tungsten oxide and their influence on tungsten oxide silicon heterojunction solar cells

Tungsten oxide WOx can be incorporated into amorphous crystalline silicon heterojunction solar cells as hole contact and for interface modification between p type amorphous silicon and indium tin oxide. This paper aims at understanding the influence of tungsten oxides properties on silicon heterojunction solar cells. Using in system photoelectron spectroscopy on thermally evaporated WOx layers, it was verified that WOx with a stoichiometry close to WO3 features a work function close to 6 eV and is therefore suitable as hole contact on silicon. Additionally the oxygen vacancy concentration in WOx was measured using photoelectron spectroscopy. High oxygen vacancy concentrations in WOx lead to a low band bending in the WOx silicon junction. Furthermore solar cells were fabricated using the same WOx, and the band bending in these cells is correlated with their fill factors FF and open circuit voltages VOC VOC . Combining these results, the following picture arises positively charged oxygen vacancies raise the Fermi level in WOx and reduce the band bending at the WOx silicon junction. This, in turn, leads to reduced VOCVOC and FF. Thus, when incorporating WOx into silicon solar cells it is important to minimize the oxygen vacancy density in WOx. Therefore deposition methods, enabling adjustment of the WOx stoichiometry are preferabl

Mitigating optical losses in crystalline silicon thin film solar cells on glass

Liquid phase crystallized silicon thin film solar cells on glass provide efficiencies up to 14.2 . While open circuit voltage and fill factor are already comparable to wafer based devices, short circuit current density is reduced due to incomplete light absorption. This paper analyzes the losses of current device designs in experiment and one dimensional simulations, revealing the low absorber thickness of 15 20 amp; 956;m as well as the planar glass silicon interface as the main cause of non absorption. Interface textures, in particular a sinusoidal texture and a smooth anti reflective three dimensional SMART texture, are discussed concerning their potential to mitigate these losses, allowing to reduce losses at the glass silicon interface by at least 40 relative. Taking the electronic interface quality into account, the SMART texture is identified as the most promising texture for light management in liquid phase crystallized silicon thin film solar cells on glas

Sinusoidal nanotextures for light management in silicon thin film solar cells

Recent progresses in liquid phase crystallization enabled the fabrication of thin wafer quality crystalline silicon layers on low cost glass substrates enabling conversion efficiencies up to 12.1 . Because of its indirect band gap, a thin silicon absorber layer demands for efficient measures for light management. However, the combination of high quality crystalline silicon and light trapping structures is still a critical issue. Here, we implement hexagonal 750 nm pitched sinusoidal and pillar shaped nanostructures at the sun facing glass silicon interface into 10 m thin liquid phase crystallized silicon thin film solar cell devices on glass. Both structures are experimentally studied regarding their optical and optoelectronic properties. Reflection losses are reduced over the entire wavelength range outperforming state of the art anti reflective planar layer systems. In case of the smooth sinusoidal nanostructures these optical achievements are accompanied by an excellent electronic material quality of the silicon absorber layer enabling open circuit voltages above 600 mV and solar cell device performances comparable to the planar reference device. For wavelengths smaller than 400 nm and higher than 700 nm optical achievements are translated into an enhanced quantum efficiency of the solar cell devices. Therefore, sinusoidal nanotextures are a well balanced compromise of optical enhancement and maintained high electronic silicon material quality which opens a promising route for future optimizations in solar cell designs for silicon thin film solar cells on glas

Improved Light Management in Crystalline Silicon Thin Film Solar Cells by Advanced Nano Texture Fabrication

We present a texturing method for liquid phase crystallized silicon thin film solar cells enabling a maximum achievable short circuit current density of 36.5mA cm 2 due to optimized light management compared to current textured device

Investigation of Band Tailing in Sputtered ZnO Al Thin Films Regarding Structural Properties and Impurities

Thin films of pure aluminum doped ZnO and with addition of nitrogen, oxygen and hydrogen have been prepared by magnetron sputtering. The spectral absorption coefficient close to the band gap energy has been determined by spectrophotometry and analyzed regarding band tailing and creation of defect bands. We found, that an improvement of Raman crystallinity under O2 rich growth conditions is not accompanied by a suppression of band tailing as expected. An additional absorption feature evolves for layers grown in N2 containing atmosphere. Doping with hydrogen attenuates sub band gap absorptio

Electronic structure of indium tungsten oxide alloys and their energy band alignment at the heterojunction to crystalline silicon

The electronic structure of thermally co evaporated indium tungsten oxide films is investigated. The stoichiometry is varied from pure tungsten oxide to pure indium oxide and the band alignment at the indium tungsten oxide crystalline silicon heterointerface is monitored. Using in system photoelectron spectroscopy, optical spectroscopy and surface photovoltage measurements we show that the work function of indium tungsten oxide continuously decreases from 6.3 eV for tungsten oxide to 4.3 eV for indium oxide, with a concomitant decrease of the band bending at the hetero interface to crystalline silicon than indium oxid

Spatial multi-criteria decision analysis to predict suitability for African swine fever endemicity in Africa

Background African swine fever (ASF) is endemic in several countries of Africa and may pose a risk to all pig producing areas on the continent. Official ASF reporting is often rare and there remains limited awareness of the continent-wide distribution of the disease. In the absence of accurate ASF outbreak data and few quantitative studies on the epidemiology of the disease in Africa, we used spatial multi-criteria decision analysis (MCDA) to derive predictions of the continental distribution of suitability for ASF persistence in domestic pig populations as part of sylvatic or domestic transmission cycles. In order to incorporate the uncertainty in the relative importance of different criteria in defining suitability, we modelled decisions within the MCDA framework using a stochastic approach. The predictive performance of suitability estimates was assessed via a partial ROC analysis using ASF outbreak data reported to the OIE since 2005. Results Outputs from the spatial MCDA indicate that large areas of sub-Saharan Africa may be suitable for ASF persistence as part of either domestic or sylvatic transmission cycles. Areas with high suitability for pig to pig transmission (‘domestic cycles’) were estimated to occur throughout sub-Saharan Africa, whilst areas with high suitability for introduction from wildlife reservoirs (‘sylvatic cycles’) were found predominantly in East, Central and Southern Africa. Based on average AUC ratios from the partial ROC analysis, the predictive ability of suitability estimates for domestic cycles alone was considerably higher than suitability estimates for sylvatic cycles alone, or domestic and sylvatic cycles in combination. Conclusions This study provides the first standardised estimates of the distribution of suitability for ASF transmission associated with domestic and sylvatic cycles in Africa. We provide further evidence for the utility of knowledge-driven risk mapping in animal health, particularly in data-sparse environments.</p