Synthesis of calcium monosilicide nanowires by reactive deposition technique

The CaSi nanowires were synthesized on Si substrate by reactive deposition technique. A great amount of Ca vapor reacted with surface of cleaned Si substrate, and CaSi nanowires was grown on the as-synthesized CaSi film. The diameter of nanowires could achieve with a minimum value about 25 nm. The CaSi nanowire was self-orient along the <001> direction. We can control the length of nanowires by experimental parameter settings, such as quantity of Ca source, duration time and temperature. The formation mechanism of Ca-silicides on Si substrate was discussed in detail. Raman spectroscopy shows that the nanosized character for CaSi phase was confirmed. Meanwhile, the Ca-silicides layer showed a strong absorption in the ultraviolet (UV) region of the solar spectrum, indicating their potential applications.

Framework structure materials in photovoltaics based on perovskites 3D

The inorganic and hybrid organic / inorganic perovskites based on lead halide and derived materials (alloys) having the formula ABX3 are emerging as a new and innovative family of absorber materials for the conversion of solar energy into electricity in photovoltaic systems. Thanks to their composition, perovskites and derivatives have exceptional optical, electrical and structural properties with high absorption of light in the visible solar spectrum and good mobility of charge carriers generated by photons facilitating the extraction of electric current. Due to these important properties, perovskite solar cells combine a high efficiency of conversion of light into electricity with great ease of preparation and synthesis at very low costs via simple deposition techniques. In this article we review the structural and optoelectronic properties of perovskites 3D exhibiting photovoltaic properties, we are also interested in the operating principle of perovskite-based solar cells, charge transport materials and associated architectures. Simple fabrication techniques and issues with stability and hysteresis are also discussed.

A Photon Force and Flow for Dissipative Structuring: Application to Pigments, Plants and Ecosystems

Through a modern derivation of Planck’s formula for the entropy of an arbitrary beam of photons, we derive a general expression for entropy production due to the irreversible process of the absorption of an arbitrary incident photon spectrum in material and its dissipation into an infrared-shifted grey-body emitted spectrum, with the rest being reflected or transmitted. Employing the framework of Classical Irreversible Thermodynamic theory, we define the generalized thermodynamic flow as the flow of photons from the incident beam into the material and the generalized thermodynamic force is, then, the entropy production divided by the photon flow, which is the entropy production per unit photon at a given wavelength. We compare the entropy production of different inorganic and organic materials (water, desert, leaves and forests) under sunlight and show that organic materials are the greater entropy-producing materials. Intriguingly, plant and phytoplankton pigments (including chlorophyll) reach peak absorption exactly where entropy production through photon dissipation is maximal for our solar spectrum 430<λ<550 nm, while photosynthetic efficiency is maximal between 600 and 700 nm. These results suggest that the evolution of pigments, plants and ecosystems has been towards optimizing entropy production, rather than photosynthesis. We propose using the wavelength dependence of global entropy production as a biosignature for discovering life on planets of other stars.

UV-visible-NIR active smart photocatalytic system based on NaYbF4:Tm3+ upconverting particles and Ag3PO4/H2O2 for photocatalytic processes under both light on/light off conditions

The development of broad-spectrum photocatalytic materials that allow the use of a larger portion (UV to NIR) of the solar spectrum for photocatalytic processes has attracted greater attention. Among the...

Visible and Infrared Solar Upconversion for Water Splitting via Surface Plasmon-passivated Strategy

The current photocatalytic technology for water splitting usually localized in specific short-wavelength photons. Herein, we used surface plasmon resonance (SPR) of noble metal to respond to a broad solar spectrum,...