Category SOLAR CELLS – NEW ASPECTS AND SOLUTIONS

Metallic nanocluster contacts for high-effective photovoltaic devices

High efficiency of solar energy conversion is a main challenge of many fields in novel nanotechnologies. Various nanostructures have been proposed early (Pillai et al., 2007; Hun et al., 2007; Johnson et al., 2007; Slaoui & Collins, 2007). However, every active element cannot function without electrodes. Thus, the problem of performing effective contacts is of particular interest.

The unique room-temperature electrical characteristics of the porous metallic nanocluster – based structures deposited by the wet chemical technology on conventional silicon-based solar cells were described in (Laptev & Khlyap, 2008). We have analyzed the current-voltage characteristics of Cu-Ag-metallic nanocluster contact stripes and we have registered for the first time dark currents in metallic structures...

Read More

Electrical properties of copper clusters in porous silver of silicon solar cells

Technologies for producing electric contacts on the illuminated side of solar cells are based on chemical processes. Silver technologies are widely used for manufacturing crystalline silicon solar cells. The role of small particles in solar cells was described previously (Hitz, 2007; Pillai, 2007; Han, 2007; Johnson, 2007). The introduction of nanoparticles into pores of photon absorbers increases their efficiency. In our experiments copper microclusters were chemically introduced into pores of a silver contact. They changed the electrical properties of the contact: dark current, which is unknown for metals, was detected.

In the experiments, we used 125 x*125-mm commercial crystalline silicon wafers Si<P>/SiNx (70 nm)/Si<B> with a silver contact on the illuminated side...

Read More

Condensate of thermal radiation

Thermal radiation is a unique thermodynamic system while the expression dU=TdS-pdV for internal energy U, entropy S, and volume V holds the properties of the fundamental equation of thermodynamics regardless the variation of the photon number (Kondepudi & Prigogin, 1998. Bazarov, 1964). Differential expression dp/dT=S/V for pressure p and temperature T is valid for one-component system under phase equilibrium if the pressure does not depend on volume V (Muenster, 1970). Thermal radiation satisfies these conditions but shows no phase equilibrium.

The determinant of the stability of equilibrium radiation is zero (Semenchenko, 1966). While the „zero" determinants are related to the limit of stability, there are no thermodynamic restrictions for phase equilibrium of radiation (Muenster, 1970)...

Read More

Thermodynamic efficiency of the photosynthesis in plant cell

It is known that solar energy for glucose synthesis is transmitted as work (Berg et al., 2010; Lehninger et al., 2008; Voet et al., 2008; Raven et al., 1999). Here it is shown for the first time that there are pigments which reemit solar photons whithout energy conversion in form of heat dissipation and work production. We found that this antenna pigments make 77% of all pigment molecula in a photosystem. Their existance and participation in energy transfer allow chloroplasts to overcome the efficiency threshold for working pigments as classic heat engine and reach 71% efficiency for light and dark photosynthesis reactions. Formula for efficiency calculation take into account differences of photosynthesis in specific cells...

Read More

Thermodynamic scale of the efficiency of chemical action of solar radiation

Radiant energy conversion has a limit efficiency in natural processes. This efficiency is lower in solar, biological and chemical reactors. With the thermodynamic scale of efficiency of chemical action of solar radiation we will be able to compare the efficiency of natural processes and different reactors and estimate their commercial advantages. Such a scale is absent in the well_known thermodynamic descriptions of the solar energy conversion, its storage and transportation to other energy generators (Steinfeld & Palumbo, 2001). Here the thermodynamic scale of the efficiency of chemical action of solar radiation is based on the Carnot theorem.

Chemical changes are linked to chemical potentials...

Read More

Antenna processes in plants

Let us leave the discussion of technological matters relating to the manipulation of antenna processes aside for the time being. We will devote a subsequent publication to this subject. Let us only remark here that the conversion of solar energy involving the participation of antenna molecules figures in the description of photosynthesis in biology. Every chlorophyll molecule in plant cells, which is a direct convertor of solar energy, is surrounded by a complex of 250­400 pigment molecules (Raven et al., 1999). The thermodynamic aspects of photosynthesis in plants were studied in (Wuerfel, 2005; Landsberg, 1977), yet the idea of antenna for solar cells was not proposed...

Read More

Antenna processes and photon cutting

A photon cutting process (Wegh et al., 1999) as photon reemission is an example for an antenna process. It includes the emission of two visible photons for each vacuum ultraviolet photon absorbed. For us important, that materials with introduced luminescent activators ensure the separation of the photon antenna reemissions and the photon work production processes. In our opinion, ultra-high efficiencies can be reached if: firstly, we solve the problem of separating the photon antenna reemissions and the photon work production processes. Secondly, one should know a way of transformation of irreversible photon antenna reemissions into reversible. Let us consider the activator states in an absorber as state 3. A photon cutting process is irreversible in case of the reemissions (1231)n...

Read More

Antenna processes and temperature of radiation

Let us call the reemission of solar energy during an antenna process retranslation, if the temperature of the radiation remains constant, and transformation, if the temperature of the radiation changes. The retranslation of radiation by a black body is, by definition, a reversible process. Transformation can take place both in a reversible and irreversible way. Therefore, the efficiency of the work performed by a solar cell can be improved by increasing the fraction of retranslating and transforming reversible antenna processes as well as working equilibrium states in an absorber.

Read More