Wyniki 1-4 spośród 4 dla zapytania: authorDesc:"Mikhail TIVANOV"

Effect of absorbing layer thickness on efficiency solar cells based on Cu(In,Ga)(S,Se)2

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On the basis of one-dimensional model of the solar cell (SC) the influence of photoactive layer thickness on the photocurrent (a key parameter for the collection efficiency of photogenerated charge carriers) of a has been studied. It is shown that for a typical Cu(In,Ga)(S,Se)2 - based SC the optimal value of the photoactive layer thickness is about 1.5 m. Reducing the thickness of the photoactive layer leads to a sharp decrease in the photocurrent and increase the series resistance. Streszczenie. Na podstawie jednowymiarowego modelu ogniwa słonecznego zbadano wpływ grubości warstwy fotoaktywnej na natężenie fotoprądu (parametru kluczowego dla ustalania sprawności fotogenerowanych nośników ładunku). Wykazano, że dla typowych ogniw słonecznych opartych o Cu(In,Ga)(S,Se)2 optymalną wartością grubości warstwy fotoaktywnej jest w przybliżeniu 1,5 m. Redukując grubość warstwy fotoaktywnej doprowadzono do gwałtownego spadku wartości fotoprądu i wzrostu rezystancji szeregowej. (Efekt absorbcji grubości warstwy na sprawność ogniw słonecznych na bazie Cu(In,Ga)(S,Se)2). Keywords: Cu(In,Ga)(S,Se)2, solar cell, absorbing layer. Słowa kluczowe: Cu(In,Ga)(S,Se)2, ogniwo słoneczne, warstwa absorbcyjna. Introduction The suitability of thin-film Cu(In,Ga)(S,Se)2 (CIGSS) solar cells (SCs) usage is shown in many studies [1-4] because these chalcopyrite compounds have shown the highest efficiencies (> 19 %) for laboratory thin film SCs. The semiconductor CIGSS material have a high value of absorption index, therefore, it is possible to use a fairly thin films in absorber layer of SC [4, 5]. This, in turn, significantly reduces material costs. The band gap in CIGSS-based solar cells can be varied from 1.0 to 2.4 eV and can be reconciled with the optimal value for the Sun radiation spectrum [6-9]. Moreover, these SCs have a very long term stability and radiation resistance [5]. It was developed many methods to produce thin films of CIGS[...]

Two-dimensional thermal conductivity of defect-free singlewalled carbon nanotubes DOI:10.15199/48.2016.08.22

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Based on the known Debye's model for heat capacity and on the kinetic model for the phonon heat transfer taking into account the length of nanotube and also of the contribution made by phonon-phonon scattering, a heat conduction model of defect-free single-wall carbon nanotube was proposed. Based on this model, the dependences of the two-dimensional thermal conductivity of defect-free single-wall carbon nanotubes on their length and temperature were defined. Streszczenie. Na podstawie modelu pojemności cieplnej Debaye'a oraz modelu cieplnego transferu fononów, biorąc pod uwagę długość nanorurki a także wkład rozpraszania fonon-fonon, zaproponowano model przewodzenia ciepła jednościennych nanorurek węglowych bez defektów. Bazując na tym modelu zdefiniowano zależności dwuwymiarowego przewodnictwa cieplnego jednościennych nanorurek węglowych bez defektów od ich długości. (Dwuwymiarowa przewodność cieplna jednościennych nanorurek węglowych bez defektów). Keywords: carbon nanotube, thermal conductivity. Słowa kluczowe: nanorurki węglowe, przewodność cieplna. Introduction Due to its good electrical and heat conductivity [1], high values of chemical, thermic and mechanical stability [1, 2], carbon nanotubes (CNTs) are one of the most promising objects of nanoelectronics [1-5]. Despite the huge potential of CNTs application in nanoelectronics as a part of heat-removing devices, known models for calculation of its thermal conductivity provide different results [6-11]. The values of CNTs thermal conductivity determined experimentally also vary significantly [12-14]. A possible reason for this discrepancy is incorrect application of three-dimensional representations of the thermal conductivity and other physical phenomena in two-dimensional structures [15]. We have developed a heat conduction model of defectfree single-wall carbon nanotube (SWСNT). This model is based on the known Debye’s model for heat capacity and on the[...]

Calculation of the ultimate efficiency of p-n-junction solar cells taking into account the semiconductor absorption coefficient DOI:10.15199/48.2016.08.23

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A model based on the famous model of Shockley-Queisser for calculation the ultimate efficiency of solar cells has been proposed, taking into account the dependence of the semiconductor absorption coefficient on the band-gap and on the energy of the incident photons. The dependence of the ultimate efficiency of solar cells on thickness of the absorption layer was found out for homogeneous solar cells. Streszczenie. Opierając się na znanym modelu Shockley`a-Queisser`a do obliczeń maksymalnej sprawności ogniw słonecznych, zaproponowano model biorąc pod uwagę zależność współczynnika absorpcji półprzewodników od pasma wzbronionego oraz energii padających fotonów. Określono zależność maksymalnej sprawności ogniw słonecznych od grubości warstwy absorpcyjnej dla jednorodnych ogniw słonecznych. (Obliczanie maksymalnej sprawności złącza p-n ogniw słonecznych na podstawie współczynnika absorpcji półprzewodników). Keywords: solar cell, ultimate efficiency of solar cells, the Shockley-Queisser limit, absorption coefficient. Słowa kluczowe: ogniwo słoneczne, maksymalna sprawność ogniw słonecznych, limit Shockley`a-Queisser`a, współczynnik absorpcji. Introduction Solar radiation has the largest potential among renewable energy sources [1,2]. The most common method of solar energy conversion into electricity is based on the use of solar cells (SCs), as it has shown promise in producing devices with a stable performance and highefficiency [2,3]. The main goal of the solar industry is to improve the efficiency of solar energy conversion into electricity by SCs. Solution of this problem requires continuous investigation of SCs which includes the study of different materials for constructing SCs and the development of the procedures of calculation the limits of efficiency of SCs. To estimate the ultimate efficiency of a solar cell the well-known model of Shockley and Queisser is commonly used. Shockley and Queisser suggested that the carrier generatio[...]

Determination of CdSxSe1-x thick films optical properties from reflection spectra DOI:10.15199/48.2016.09.23

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Abstract. A method for determining the band gap value and the refractive index near the absorption edge from reflection spectra was tested for CdSxSe1-x films prepared using the screen-printing and sintering technique. Streszczenie: Przeanalizowano metodę wyznaczenia szerokości przerwy energetycznej i współczynnika załamania z pomiarów widma współczynnika odbicie warstw CdSxSe1-x otrzymanych metodami sitodruku i konsolidacji termicznej (sintering technique). (Wyznaczanie parametrów optycznych grubych warstw CdSxSe1-x z analizy widma odbicia). Keywords: semiconductors, CdSxSe1-x thick films, refractive index, reflection spectra. Słowa kluczowe: półprzewodniki, warstwy CdSxSe1-x, współczynnik załamania, widmo odbicia. Introduction The development of optoelectronics stimulates research of the photoelectric and optical properties of semiconductor films used in different optoelectronic devices [1-4]. The refractive index and the band gap value are some of the most important optical parameters of semiconductor films [5-6]. A method to determine the band gap value and the refractive index near the absorption edge of the thick films of semiconductor materials from optical reflection spectra, measured at different angles of incidence of the optical radiation, is theoretically justified and experimentally implemented in the present study. Verification of this method for CdSxSe1-x films of solid solution prepared using the screen-printing and sintering technique was done in the present work [7-9]. The direct band gap semiconductors like CdS, CdSe and their solid solutions are excellent materials for the development of optoelectronic and photovoltaic devices due to their high absorption coefficients and appropriate band gap [9-11]. A simple screen-printing method can be suitable for the production of low-cost large-area photosensitive devices [7-9]. Theory Let d be the thickness of the semiconductor film with a surface roughness smaller t[...]

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