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Detekcja kanałów bocznikujących w cienkowarstwowych ogniwach fotowoltaicznych z wykorzystaniem badań termowizyjnych

Cieślak K., Gułkowski S., Olchowik J., Kozak B., Wiśniewski M.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2012

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z. 59, nr 2/II/I

131-136

PL

W artykule przedstawiono analizę badań termowizyjnych do detekcji kanałów bocznikujących w cienkowarstwowych ogniwach fotowoltaicznych. Analizowane ogniwa słoneczne zostały wytworzone na bazie cienkich, monokrystalicznych warstw krzemowych. Warstwa krzemu została nanoszona na podłoże przy zastosowaniu metody epitaksji z fazy ciekłej (Liquid Phase Epitaxy – LPE) [1] i stanowiła warstwę aktywną ze złączem p-n w ogniwie słonecznym. Ze względu na specyfikę wzrostu, na brzegach warstw mogą pojawiać się kanały bocznikujące, co powoduje spadek wydajności fotoogniw. Żeby zlokalizować i wyeliminować niekorzystne obszary fotoogniwa, w badaniach zastosowano analizę termowizyjną powierzchni fotoogniw i ablację laserową [2].

EN

Solar cells were fabricated on the base of thin silicon monocrystalline layers obtained in liquid phase epitaxy process (LPE). Modification of LPE was introduced – growing substrate was covered with SiO2 and growing windows was opened in dielectric cover. Specificity of growth on that kind of substrate introduces some crystallographic defects on the edge of the sample. After solar cells fabrication these deformations can make “hot spots” which decrease solar cell performance. In order to localize this areas infrared thermography examination was introduced and UV laser was used to eliminate it from a solar cell.

2

Influence of dielectric coverage on photovoltaic conversion of silicon solar cells obtained by epitaxial lateral overgrowth

Cieslak K., Gulkowski S., Olchowik J. M.

Materials Science Poland

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2012

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Vol. 30, No. 3

274--277

EN

This work presents an analysis of the influence of SiO2 dielectric coverage of a Si substrate on the solar-cell efficiency of Si thin layers obtained by epitaxial lateral overgrowth (ELO). The layers were obtained by liquid phase epitaxy (LPE). All experiments were carried out under the following conditions: initial temperature of growth: 1193 K; temperature difference ^T = 60 K; ambient gas: Ar; metallic solvent: Sn+Al; cooling rates: 0.5 K/min and 1 K/min. To compare the influence of the interior reflectivity of photons, we used two types of dielectric masks in a shape of a grid etched in SiO2 along the <110> and <112> directions on a p+ boron-doped (111) silicon substrate, where silicon dioxide covered 70 % and 80 % of the silicon surface, respectively. The results obtained in this work depict the correlation between the interior efficiency and percentage of SiO2 coverage of the substrate of the ELO solar cells.

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Finite element method simulation of interface evolution during epitaxial growth

Gulkowski S., Olchowik J. M., Cieslak K., Moskvin P. P.

Materials Science Poland

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2012

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Vol. 30, No. 4

414--418

EN

Epitaxial Lateral Overgrowth (ELO) is a method of epitaxial growth on a partially masked substrate. It can be a promising method for photovoltaic applications due to a possibility of producing thin and high quality silicon substrates. Since the mask prevents propagation of the substrate dislocations to the laterally overgrown parts of the ELO layer they are characterized by a lower dislocation density than the substrate. It means that it is possible to fabricate good quality solar cells on a poor quality Si substrate. The main goal of the research is to obtain a higher growth rate in the lateral direction than in the direction normal to the substrate. The epilayer growth kinetics depends on many technological factors, basically the growth temperature, the cooling rate, the solvent and the mask filling factor. For this reason the best way to achieve the goal is a computational analysis of the epitaxial layer growth process. This work presents a two-dimensional computational study of such a process of growth for different technological conditions. The computational model is based on the assumption of pure diffusion control growth.

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Modelling of the Interface Evolution During Si Layer Growth on a Partially Masked Substrate

Gulkowski S., Olchowik J., Cieślak K., Moskvin P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2011

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Vol. 15, No 1

91-98

EN

High-quality thin Si layers obtained from the solution by epitaxial lateral overgrowth (ELO) can play a crucial role in photovoltaic applications. The laterally overgrown parts of the layer are characterized by a lower dislocation density than that of the substrate. The height and width of the layer depend on several factors, such as the technological conditions of liquid phase expitaxy (LPE), growth temperature, cooling rate and the geometry of the system (mask filling factor). Therefore, it is crucial to find the optimal set of technological parameters in order to obtain very thin structures with a maximum width (high aspect ratio). This paper presents a computational study of Si epilayer growth on a line-pattern masked silicon substrate from Si-Sn rich solution. To solve this problem, a mixed Eulerian-Lagrangian approach was applied. The concentration profile was calculated by solving the two-dimensional diffusion equation with appropriate boundary conditions. The growth velocity was determined on the basis of gradients of concentration in the border of the interface. Si interface evolution from the opened window was demonstrated.

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Wpływ wewnętrznego lustra na wydajność kwantową fotoogniw wytwarzanych w oparciu o krzemowe warstwy lateralne

Cieślak K., Olchowik J. M., Gułkowski S.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 4

20-21

PL

W pracy przedstawiono rezultaty badań krzemowych ogniw słonecznych, wytwarzanych za pomocą, epitaksji z fazy ciekłej LPE (Liquid Phase Epitaxy). Epitaksja z fazy ciekłej pozwala w ekonomiczny sposób uzyskiwać cienkie monokrystaliczne warstwy, które mają również zastosowania w fotowoltaice. W prowadzonych badaniach zastosowano pewną modyfikację klasycznej metody LPE - wzrost na częściowo maskowanym dielektrykiem podłożu krzemowym. Taki sposób nosi nazwę epitaksji lateralnej ELO (Epitaxial Lateral Overgrowth) i pozwala na uzyskanie warstw o znacznie mniejszej gęstości defektów w stosunku do gęstości defektów w podłożu wzrostowym [1], co więcej warstwa dielektryka obecna wewnątrz struktury fotoogniwa stanowi lustro dla niezaabsorbowanych fotonow, co pozwala na wydłużenie ich drogi optycznej. W pracy porównano wpływ wewnętrznego lustra z dielektryka SiO₂ na wydajność kwantową, badanych fotoogniw.

EN

This work contains research of silicon thin film solar cells obtained from a lateral overgrowth liquid phase epitaxy (LPE). Liquid phase epitaxy is an economic method that enables to produce thin, monocrysallic films for photovoltaic applications. Presented research are based on some modification of the LPE method - it uses partially masked by dielectric, growing silicon substrates. This modification is called epitaxial lateral overgrowth (ELO) and enables to obtain lower defects density in a growing layer comparing to a growing substrate [1]. Moreover dielectric layer inside a solar cell structure forms an inner mirror for photons which are not absorbed in the active layer. This work presents influence of the inner mirror formed from SiO₂ efficiency of the solar cells.

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Modelling of thin Si layers growth on partially masked Si substrate

Gułkowski S., Olchowik J.M., Jóźwik I., Moskvin P.P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2008

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Vol. 12, No 1-2

121-126

EN

This paper presents a numerical simulation of epitaxial lateral overgrowth of silicon layers from the liquid phase of an Sn solvent. A two-dimensional diffusion equation has been solved and the concentration profiles of Si in a Si-Sn rich solution during the growth have been constructed. The epilayer thickness and width have been obtained from the concentration near the interface.

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Strain in epitaxial laterally overgrown structures

Zytkiewicz Z. R.

Opto-Electronics Review

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2001

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Vol. 9, No. 2

142-149

EN

X-ray diffraction and synchrotron x-ray topography methods were used to analyse strain in GaAs layers grown on GaAs and Si substrates by epitaxial lateral overgrowth (ELO) from a liquid phase. We show the laterally overgrown parts of ELO stripes adhere to the SiO₂ mask which results in their downwards bending. The procedure was found which allows to control adhesion of the layers to the mask by adjusting the vertical growth rate of the layers. For the case of GaAs ELO layers grown on Si substrates the ELO stripes bend outwards from the mask due to the tensile strain in the GaAs buffer layer. Recent data published on strain in other than GaAs ELO structures are reviewed and compared with our results.