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1
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Limitations on Thickness of Absorber Layer in CdS/CdTe Solar Cells

100%
Mykytyuk T., Roshko V., Kosyachenko L., Grushko E.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1073-1076
EN
Calculations of the integrated absorptive capacity of CdTe layer taking into account the spectrum of the AM1.5 solar radiation and the absorption coefficient of CdTe are carried out. The recombination losses at the front and rear surfaces of the CdTe layer and in the space-charge region are also calculated based on the continuity equation. The restrictions on the thickness of CdTe in CdS/CdTe heterojunction have been ascertained taking into account all types of losses. It is shown that in CdTe, the almost complete absorption of photons (99.9%) in the hν > E_{g} range is observed at a layer thickness of more than 20-30 μm, and the absorptive capacity of photons in a CdTe layer of thickness 1 μm is about 93%. The obtained results indicate that when the CdTe absorber layer is very thin, it is impossible to avoid a noticeable decrease of the short circuit current density J_{sc} as compared with a typical thickness of the absorber layer. The loss in J_{sc} is 19-20% when the thickness is 0.5 μm compared to 5% for a thickness of 2-3 μm.
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Spectral Distribution of Photoelectric Efficiency οf Thin-Film CdS/CdTe Heterostructure

100%
Kosyachenko L., Lashkarev G., Grushko E., Ievtushenko A., Sklyarchuk V., Mathew X., Paulson P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
862-864
EN
The spectral distribution of the quantum efficiency in thin-film CdS/CdTe solar cells is being investigated by taking into account the drift and diffusion components of photocurrent, recombination at the CdS-CdTe interface, the back surface of the CdTe absorber layer and in the space-charge region. The effect of uncompensated acceptor concentration, lifetime of minority carriers and surface recombination velocity on the charge collection efficiency are discussed. The losses caused by reflections and absorption in the CdS and indium tin oxide layers are also considered.
3
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The Effect of Surface Preparation on Physical Properties of Ni-ZnSe Junctions

100%
Chusnutdinow S., Makhniy V., Aleszkiewicz M., Zaleszczyk W., Slotov M.
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vol. 126
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issue 5
1076-1078
EN
We report on optical and photovoltaic properties of Ni-ZnSe junctions. We demonstrate that the preparation method of the ZnSe surface determines luminescence, optical transmission of ZnSe substrates and photovoltaic spectra of the Ni-ZnSe junctions. The observed effects are explained by formation of low-dimensional quantum structures on the ZnSe surface in result of the surface preparation procedure. This is confirmed by atomic force microscopy studies, which show the presence of grains with lateral dimensions of 30-300 nm on ZnSe surface. The smallest grains are responsible for a wide spectral band observed in photoluminescence at 3.4 eV, i.e., at much higher energies than the energy gap of bulk ZnSe, E_{g} ≈ 2.7 eV.
4
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Reduction of the Optical Losses in CdTe/ZnTe Thin-Film Solar Cells

100%
Chusnutdinow S., Pietruszka R., Zaleszczyk W., Makhniy V., Wiater M., Kolkovsky V., Wojtowicz T., Karczewski G.
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vol. 126
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issue 5
1072-1075
EN
We report on reduction of optical losses in n-CdTe/p-ZnTe thin-film solar cells grown by molecular beam epitaxy. The investigated thin-film devices were grown from elemental sources on monocrystalline, semi-insulating, (100)-oriented GaAs substrates. The optical losses have been reduced by a texturing of the device surface and by depositing of a ZnO antireflection coating. Current-voltage and spectral characteristics of the investigated p-ZnTe/n-CdTe solar cells depend significantly on the preparation of the surface of the ZnTe window. We describe a procedure of chemical etching of the ZnTe window leading to surface texturing. A ZnO layer of proper thickness deposited by low-temperature atomic layer deposition technique on the ZnTe surface forms an effective antireflection coating that leads to the reduction of optical losses. Due to reduction of the optical losses we observe increase of the short-circuit current, J_{SC}, by almost 60% and of the energy conversion efficiency by 44%.
5
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Detector with High Internal Photocurrent Gain Based on ZnO:N

100%
Kosyachenko L., Lashkarev G., Ievtushenko A., Lazorenko V., Sklyarchuk V., Sklyarchuk O.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
681-682
EN
The photoresponsive structures prepared by magnetron sputtering of ZnO:N on p-Si substrates followed by vacuum evaporation of semi-transparent Ni film on ZnO surface were investigated. The mentioned structures show high sensitivity that sharply enhances with increase of applied voltage. Under a bias 5 V, the responsivities at λ = 390 and 850 nm are equal to 210 A/W and 110 A/W which correspond to the quantum efficiencies of 655 and 165, respectively. It is suggested that the observed high response is attributed to internal gain in phototransistor structure containing Ni/n-ZnO Schottky contact as emitter junction and n-ZnO/p-Si heterostructure as collector junction.
6
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Theoretical Analysis of Optical Losses in CdS/CdTe Solar Cells

100%
Roshko V., Kosyachenko L., Grushko E.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
954-956
EN
Based on the known refractive index and extinction coefficient, calculations of optical losses in glass/transparent conducting oxide/CdS/CdTe solar cells have been carried out taking into account reflections at the interfaces and absorption in the transparent conducting oxide (indium tin oxide or SnO_2:F) and CdS layers. It has been shown that the losses caused by reflections at the interfaces result in lowering the short-circuit current by ≈ 9% whereas absorption in the transparent conducting oxide and CdS layers with the typical thicknesses lead to losses of 15-16% for glass/SnO_2/CdS/CdTe, and 22-24% for glass/indium tin oxide/CdS/CdTe solar cells.
7
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Ultraviolet Detectors Based on ZnO:N Thin Films with Different Contact Structures

100%
Ievtushenko A., Lashkarev G., Lazorenko V., Karpyna V., Sichkovskyi V., Kosyachenko L., Sklyarchuk V., Sklyarchuk O., Bosy V., Korzhinski F., Ulyashin A., Khranovskyy V., Yakimova R.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1123-1129
EN
Al/ZnO:N/Al and Ni/ZnO:N/Al diode photodetectors fabricated by dc magnetron sputtering of ZnO:N films on p-Si substrates are studied. The photocurrent-to-dark current ratio equal to 250 at λ= 390 nm and the time constant of photoresponse about 10 μs for Al/ZnO:N/Al structures with 4 μm interdigital spacing was achieved. The Ni/ZnO:N/Al diode structure has the rectification ratio ≈10² at bias 1 V, the maximal responsivity about 0.1 A/W is observed at 365 nm, and the measured time constant of photoresponse is about 100 ns.
8
Content available remote

Electrical Properties of GaInAsSb/GaSb/GaAlAsSb Double Heterostructure with Low Diameter

100%
Kucur B., Ahmetoglu M., Andreev I., Kunitsyna E., Mikhailova M., Yakovlev Y.
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vol. 125
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issue 2
411-413
EN
GaInAsSb/GaSb/GaAlAsSb double heterostructures are attractive for optoelectronic devices working in the 1.5-4.8 μm wavelength region. In this paper, the current mechanisms of liquid phase epitaxy grown GaInAsSb based double heterostructures with 100 μm diameter were investigated in the temperature range 77-350 K. It was found that diffusion current dominates at the high temperature (> 240 K) and small forward bias region, while generation-recombination current dominates at intermediate temperatures (242-171 K). At low temperature region (< 171 K), the tunneling mechanism of the current flow dominates in both forward and reverse biases.
9
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Peculiarities of High Power Infrared Detection on Narrow-Gap Semiconductor p-n Junctions

100%
Gradauskas J., Širmulis E., Ašmontas S., Sužiedėlis A., Dashevsky Z., Kasiyan V.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
237-240
EN
We report on experimental results of photosignal investigation in HgCdTe, InSb and PbTe semiconductor p-n junctions under the action of an intense pulsed CO_2 laser. The influence of laser power, external bias voltage as well as the diode temperature on the photosignal formation has been studied. We show that under certain conditions both classical photovoltaic and hot carrier phenomena may act simultaneously within a junction thus strongly impacting on responsivity and speed of operation of the device. The drawn conclusions may be of great importance for the development of high power optoelectronic devices.
10
Content available remote

Electrical Properties of p-ZnTe/n-CdTe Photodiodes

100%
Chusnutdinow S., Makhniy V., Wojtowicz T., Karczewski G.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1077-1079
EN
Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of photovoltaic, thinfilm p-ZnTe/n-CdTe heterojunctions have been studied in the temperature range of 280-400 K. The p-n junctions were grown by MBE on (100) semi-insulating GaAs substrates. From the analysis of I-V and C-V curves the potential barrier height of the junctions and its temperature dependence are determined. The relatively large value of the temperature coefficient of the potential barrier height (2.5-3.0 × 10^{-3} eV/K) indicates a high density of defects at the p-ZnTe/n-CdTe interface. The presence of interface defects limits the efficiency of the solar energy conversion of these devices.
11
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Content available

Semiconductor Materials for Ultrafast Photoswitches

75%
Coutaz J.
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issue 4-5
495-512
EN
This paper gives a review of semiconductor materials that are used to fabricate ultrafast photoswitches. The optoelectrical response of the switches is first described with simple models, from which the material requirements are deduced. The basic principles of the required material properties - ultrashort free carrier lifetime and high mobility, high dark resistivity, and high field breakdown - are explained. Then, the most popular ultrafast semiconductors are listed, together with their characteristics. A special emphasis is put on low-temperature grown GaAs. Finally, two applications of these ultrafast materials are presented, namely antennae for terahertz radiation and all-optical nonlinear devices.
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