Effects of the enhancement of photoconductivity in 2D photonic macroporous silicon structures were investigated. Dependence of photoconductivity on the angle of incidence of the electromagnetic radiation is observed with maxima at normal incidence of electromagnetic radiation, in the region of the angle of full internal reflection respective to macropore walls and at a grazing angle of incidence respective to the surface of structure. The absolute maximum of photoconductivity is measured at distance between macropores, corresponding to two lengths of the electron free run, i.e. by the maximal transfer of the amplified electric components from a macropore surface in a silicon matrix. Angular dependences of photoconductivity, as well as enhancement of the photoconductivity in comparison with monocrystal silicon, primary absorption p-component of electromagnetic radiation testified to formation of surface electromagnetic waves in illuminated macrporous silicon structures. Its effects result in amplification of a local electric field on a surface of macroporous silicon structure and a macropore surface. The measured value of the built-in electric field on a macropore surface achieves 1 06 V/cm, the signal of photoconductivity amplifies 1 02 times, and Raman scattering -up to one order of value.
Polaritonic resonancies are investigated in 2D silicon photonic crystals. Theoretically unpredicted reduction in the transmittance of electromagnetic radiation and the step formation are observed for wavelengths less than optical period of structures due to directed and decay optical modes formed by macroporous silicon as a short waveguide structure. Prevalence of absorption over reflection of light testify to the polaritonic type band formation. Surface polaritons are formed on decay modes in a silicon matrix or macropore at formation of directed optical modes relatively on macropore or silicon matrix. Absorption, photoconductivity and Raman scattering maxima are determined by a corresponding maximum of a longitudinal component of electromagnetic waves in macroporous silicon structure as short waveguide with a specific surface. Longitudinal component of electromagnetic waves in investigated structure interacts effectively with surface oscillators, and polaritonic resonances in 2D silicon photonic crystals are observed.
We have proposed a new technological solution for the creation of solar energy elements using bilateral structures of macroporous silicon to increase the overall efficiency of converting light energy into electricity. Recently, the research on R&D in solar cell technology has focused mainly on crystalline silicon technologies and photovoltaic systems, including organic ones. The main physical phenomenon that determines the prospects of two-dimensional structures of macroporous silicon with nanocoatings as solar cells is the increase in absorption of electromagnetic radiation and photoconductivity as a result of interaction of optical modes with the developed surface of cylindrical macropores with a barrier on the nanocoating-surface boundary. We fabricated two-sided macroporous silicon structures with nanocoatings for solar cells, including silicon technology, organic nanoformations, and photovoltaic system formation. Silicon is a promising material for the manufacture of structures with a cylindrical geometry of air macropores due to the anisotropy of the cheap process of photoelectrochemical etching. The presence of periodically located cylindrical pores separated by silicon columns provides a large effective surface of the samples and enhanced optical and photophysical characteristics of silicon structures. Polymer composites with nanocoatings with CdS nanocrystals and multilayer carbon nanotubes in polyethyleneimine generate charges of opposite sign on both surfaces of the structures under illumination. The formation of bilateral structures of macroporous silicon with nanocoatings increases the overall energy conversion efficiency in solar cells by up to 60 %. In addition, one can use our proposed solar cells in the upper atmosphere.
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