The technology of receiving of electric energy by means of photo-electric modules is today examined as one of the most perspective methods of the use of renewable energy of sun radiation. History of development of the photo-electric modules counts three generations of sun power engineering. They are related to the productions of different types of photovoltaic materials, with a search of the ways of increase of quantum efficiency of sun sell and of decline of their cost. The first generation of photovoltaic modules is characterized by the use of the crystalline silicon (Si). Serial elements from monocrystalline silicon have relatively high (near 14….16%) efficiency of transformation of solar energy into electric one, but they cost expensively.

The second generation is characterized by introduction of polycrystalline or amorphous materials. The polycrystalline elements on the basis of polycrystalline silicon are cheaper in comparison with monocrystalline elements, but have smaller output-input ratio (11%).

Thin-film PV technologies gave birth to the third generation of the sun modules. In experimental development and on the stages of permanent improvement are found thin-film crystalline silicon (c-Si), cadmium telluride/sulfide (CTS), copper indium selenide (often abbreviated "CIS"), copper indium gallium (di)selenide (CIGS) and nanocrystalline electrochemical photo-electric elements sensibilised by dye. The serial thin-film elements require small quantity of semiconductor material and provide efficiency of transformation of sun energy into electric one at level of 8…10%.

The compounds A₂V₂, A₃V₅ are also used as the photosensitive materials. The world record of output-input ratio of the sun modules on semiconductor compounds III-V is equal 35%.

The high cost of photosensitive elements and comparatively low power efficiency prevent to the wide introduction of sun modules, that because sun elements look less concurentive in comparison with other traditional systems of power engineering.

Long expectations of appearance of the cheap and energy effective sun modules entailed certain skepticism in the relation of perspective of the systems of solar power engineering and, even, impelled to the search of adequate replacement of «obstinate» sun energy.

But specialists consider the potential of solar power engineering as extraordinarily promising, subject to the condition of the use of principally new scheme and technological decisions at development of the sun modules.

The researchers of Nizhyn Laboratories of Scanning Devices, headed by Vasil Sidorov, candidate of technical sciences, are developing an extraordinarily interesting method of modernization of the photovoltaic modules, which is based on the use of the phenomenon of quantum-electronic resonance for the increase of transitions of charges during of photo-electric transformations.

The construction of a new energy effective sun element, which is based on the photoelectric current amplification by stimulated emission of radiation, differs sufficiently from the construction of the semiconductor photovoltaic element largely known to wide society. The principle of work of well known photovoltaic сell is based on a barrier-layer photoeffect that is appearing in the origin of EMF near the contact between the two semiconductors of p- type and n-type. Such contact has the one-sided conductivity that is related to impoverishment of layers of semiconductors adjoining to the contact, by the transmitters of current (electrons, holes). An internal photoeffect in semiconductors causes violation of the permanent distribution of transmitters of current in the region of contact and results in appearance of contact difference of potentials, in other words, of electromotive force (photo- EMF). The value of photo- EMF is proportional to the intensity of light; the quantum efficiency in general is determined by spectral composition of sun radiation. Thus maximal efficiency is achieving at the irradiation of photocell by the monochromatic light of certain wave-length. Taking into account that the sun radiates in the wide range of light-spectrum (0,32…32 µm), in the real conditions only the narrow region of sunlight takes part in the creation of useful photo-electric current, the other radiation is responsible for the thermal effects that diminish energy effectiveness of the sun modules.

In opinion of researchers, for the increase of output of transmitters of charge (electrons and holes) in the new energy effective photocell the artificial system of channeling of optical quasi-monochromatic radiation can be used. In optimum case such radiation is to be monochromatic and mast to provide maximal absorption of photons by the atoms of crystalline grate.

With the purpose of receiving of generation of the coherent radiation (lasing effect) the developers must create the special state of crystal (photo-electric and simultaneously luminescent) with the population inversion. The similar state is achieving in semiconductor lasers by the injection of transmitters of charge or by pumping of electromagnetic resonator with the optical beam.

For this purpose in the structure of the sun module the certain amount of semiconductor elements is integrated; in each element the two parallel flat surfaces form an optical resonator (coefficient of reflection from the surfaces of crystal – 1,0). With the use of the some complicated geterostructure elements it is possible to attain considerably greater concentration of electron-hole pairs in an active layer and accordingly to receive greater optical gain, than in a semiconductor laser on (p-n) – transition. Other advantage of geterostructure –the retaining of the radiation that spreads along a structure within the limits of dielectric wave-guide active layer. Thanks to this factor the optical gain is used more effectively.

Thus, the channeling of optical radiation in an electromagnetic resonator provides the light amplification by stimulated emission of radiation of certain wave-length and accordantly the amplification of photo-electric current of photovoltaic cell.

Combination of physical principles and technologies of construction of photo-electric sun elements and semiconductor lasers allows creating the high effective photosensitive structures of the sun modules with quantum efficiency 50…70 % and higher, depending on the type of semiconductor. The part of irradiative acts of recombining in Si is not considerable, but in some clean semiconductors, for example, GaAs, CdS, she can in theory attain 100%.

Vasil Sidorov on April 08, 2010 from Technopark QUELTA

in Queltanews. sidorovvasil@gmail.com