ZnO layers in application as TCL for new generation of solar cells

W ciągu ostatnich lat fotowoltaika wkroczyła na drogę bardzo dynamicznego rozwoju co przekłada się na gwałtowny wzrost wielkości produkcji ogniw słonecznych. Jednocześnie rosnący procent rynku stanowią cienkowarstwowe przyrządy nowej generacji o niskiej cenie i elastycznej konstrukcji. Do pełnego wykorzystania ich zalet w tym potencjalnej elastyczności struktury konieczna jest adaptacja odpowiednich transparentnych warstw przewodzących TCL (ang: Transparent Conductive Layers). Do grupy materiałów o potencjalnych korzystnych właściwościach z punktu wykorzystania w roli elektrody transparentnej należą odmiany tlenku cynku. Prezentowana praca jest poświęcona badaniom właściwości cienkich warstw ZnO:Al wytworzonych metodą PLD (ang: Pulsed Laser Deposition) do zastosowań w charterze transparentnej elektrody przewodzącej elastycznych, cienkowarstwowych ogniw słonecznych. Opis technologii wytwarzania jest uzupełniony o wszechstronną analizę parametrów mechanicznych i optoelektronicznych uzyskanych warstw na podłożach elastycznych i sztywnych. Zaprezentowane są modele numeryczne prototypowych konstrukcji ogniw. Przedstawione są również pierwsze wyniki pomiarów eksperymentalnej konstrukcji ogniwa słonecznego wyposażonego w otrzymaną warstwę.Rapid development of photovoltaics, which may be recently observed, is transferred to a mass-production scale of PV industry. At the same time constant growth of inexpensive thin-film, flexible devices leads to their significant share in the PV market. However, the potential profits of thin film applications are limited by proper technology and materials adaptation. Important element for most of these devices is a transparent electrode made of appropriate Transparent Conductive Layer (TCL). This paper is dedicated to practical investigation of ZnO:Al layer prepared by Pulsed Laser Deposition (PLD) technology as the emitter electrode of thin film solar cells. The production technology description is detailed and supplemented by mechanical and opto-electrical parameters measurements and simulations. Described layer is prepared and examined on traditional and transparent flexible substrates as well. The concepts and first realization of the new cell structure are given

Improvement of solar cell efficiency using a luminescent top layer of ZnO nanoparticles

International audienceno abstrac

Intense visible emission from the controlled defects in ZnO nanoparticles for energy down-shifting applications in solar cells

International audienceno abstrac

Zinc oxide nanostructures with intentionally introduced defects as material for solar energy and sensing applications

International audienceMost of the existing photovoltaic (PV) solar cells are already optimized in terms of their absorption and conversion efficiency, however any strategy that can help to raise their efficiency is welcome, especially if it is cheap and does not require any modification of the solar cell fabrication technology. One possibility to increase solar cell's efficiency is the use of a material that could convert the high energy photons from the sun spectrum, namely UV and blue light, which are otherwise inefficiently absorbed by the amorphous Si, CdTe, CIGS and organic PV cells, and re-emit them as lower energy photons, for which the conversion efficiency of these cells is optimal. This so-called “down-shifting”. We study down-shifting materials based on ZnO nanoparticles. It naturally absorbs the blue and UV light thanks to a wide band gap of about 3.37 eV and it can also emit visible light, from yellow to red, depending on the nature of the crystalline and surface defects involved in the emission process. We present a quick and convenient chemical solution approach to get unique mesospheric self-assembly hybrid ZnO system with intense photoluminescent quantum yield of 40-75 % and stable visible emissions. Furthermore, the possibility of application of other ZnO nanostructures, namely zinc oxide nanowires, in gas sensors, is presented. Their excitonic and visible emission is studied in the presence of gas vapors and the results demonstrate the change of the visible photoluminescence of ZnO nanowire array and that the material is able to adsorb gases

Solution-processed zinc oxide nanostructures for solar energy and sensing applications

International audienceMost of the existing photovoltaic (PV) solar cells are already optimized in terms of their absorption and conversion efficiency, however any strategy that can help to raise their efficiency, even slightly, is welcome, and all the more if it is cheap and does not require any modification of the solar cell fabrication technology. One possibility to increase solar cell’s efficiency is the use of a material that could convert the high energy photons from the sun spectrum, namely UV and blue light, which are otherwise inefficiently absorbed by the amorphous Si, CdTe, CIGS and organic PV cells, and re-emit them as lower energy photons, for which the conversion efficiency of these cells is optimal. This so-called “down-shifting” strategy belongs to the “add-on” technology, as the aim is to fabricate a thin layer of the down-shifting material on top of the existing solar cells and all this at low cost. The criteria which a good down-shifting material needs to fulfill are: having a large Stoke shift (i.e. a discrepancy between the absorption and emission energies) and possessing high photoluminescence quantum yield (PL QY). Furthermore, this material has to be environmental-friendly and cheap. Several attempts were reported in the literature aiming at the fabrication of such a material. For example, CdS and CdSe nanoparticles embedded in polymers or silica have proved to be efficient but not necessarily cheap and non-toxic. However, high PL QY, stable green/yellow emission and easy scale–up process are expected for industrial applications. We study down-shifting materials based on ZnO nanoparticles. ZnO is a low cost, abundant and non-toxic material. It naturally absorbs the blue and UV light thanks to a wide band gap of about 3.37 eV at room temperature. ZnO can also emit visible light, from yellow to red, depending on the nature of the crystalline and surface defects involved in the emission process. Although the nature of these defects is still under debate, it is widely admitted that reducing the size down to the nanoscale enhances the presence of the defects and the luminescence efficiency of ZnO nanostructures in the visible. We present a quick and convenient chemical solution approach to get unique mesospheric self-assembly hybrid ZnO system with intense photoluminescent quantum yield of 40-75 % and stable visible emissions. We develop luminescent layers of ZnO nanoparticles dispersed and embedded in a polymer matrix to be used as down-shifting materials in the structures of solar cells. Our luminescent ZnO layers are fabricated using an easy scale–up process, which is easily adaptable for industrial applications. We will also present the parameters influencing the luminescent efficiency of chemically synthesized ZnO nanoparticles used as down-shifting material. The issue of the optimization of the luminescence EQE, in conjunction with the nano- and mesostructure of the material will also be addressed. We will show how the chemical synthesis parameters influence the ZnO nanoparticle’s EQE and how they can be adjusted to reach EQE as high as 75 %. The possibility to disperse and embed the nanoparticles in polymers (for example PMMA) will also be discussed. Furthermore, the possibility of application of other ZnO nanostructures, namely zinc oxide nanowires, in gas sensors, is presented. These nanowires are fabricated by a simple and low-cost process - chemical bath deposition. They have similar luminescent properties as studied ZnO nanoparticles, i.e. they emit in the UV and in the visible spectral range, thanks to the defects and surface states. Their excitonic and visible emission is studied in the presence of gas vapors and the results demonstrate the change of the visible photoluminescence of ZnO nanowire array and that the material is able to adsorb gases. Finally, the mechanism of gas sensing is discussed

Zinc oxide nanostructures with intentionally introduced defects as material for solar energy and sensing applications

International audienceMost of the existing photovoltaic (PV) solar cells are already optimized in terms of their absorption and conversion efficiency, however any strategy that can help to raise their efficiency is welcome, especially if it is cheap and does not require any modification of the solar cell fabrication technology. One possibility to increase solar cell's efficiency is the use of a material that could convert the high energy photons from the sun spectrum, namely UV and blue light, which are otherwise inefficiently absorbed by the amorphous Si, CdTe, CIGS and organic PV cells, and re-emit them as lower energy photons, for which the conversion efficiency of these cells is optimal. This so-called “down-shifting”. We study down-shifting materials based on ZnO nanoparticles. It naturally absorbs the blue and UV light thanks to a wide band gap of about 3.37 eV and it can also emit visible light, from yellow to red, depending on the nature of the crystalline and surface defects involved in the emission process. We present a quick and convenient chemical solution approach to get unique mesospheric self-assembly hybrid ZnO system with intense photoluminescent quantum yield of 40-75 % and stable visible emissions. Furthermore, the possibility of application of other ZnO nanostructures, namely zinc oxide nanowires, in gas sensors, is presented. Their excitonic and visible emission is studied in the presence of gas vapors and the results demonstrate the change of the visible photoluminescence of ZnO nanowire array and that the material is able to adsorb gases

Solution-processed zinc oxide nanostructures for solar energy and sensing applications

International audienceMost of the existing photovoltaic (PV) solar cells are already optimized in terms of their absorption and conversion efficiency, however any strategy that can help to raise their efficiency, even slightly, is welcome, and all the more if it is cheap and does not require any modification of the solar cell fabrication technology. One possibility to increase solar cell’s efficiency is the use of a material that could convert the high energy photons from the sun spectrum, namely UV and blue light, which are otherwise inefficiently absorbed by the amorphous Si, CdTe, CIGS and organic PV cells, and re-emit them as lower energy photons, for which the conversion efficiency of these cells is optimal. This so-called “down-shifting” strategy belongs to the “add-on” technology, as the aim is to fabricate a thin layer of the down-shifting material on top of the existing solar cells and all this at low cost. The criteria which a good down-shifting material needs to fulfill are: having a large Stoke shift (i.e. a discrepancy between the absorption and emission energies) and possessing high photoluminescence quantum yield (PL QY). Furthermore, this material has to be environmental-friendly and cheap. Several attempts were reported in the literature aiming at the fabrication of such a material. For example, CdS and CdSe nanoparticles embedded in polymers or silica have proved to be efficient but not necessarily cheap and non-toxic. However, high PL QY, stable green/yellow emission and easy scale–up process are expected for industrial applications. We study down-shifting materials based on ZnO nanoparticles. ZnO is a low cost, abundant and non-toxic material. It naturally absorbs the blue and UV light thanks to a wide band gap of about 3.37 eV at room temperature. ZnO can also emit visible light, from yellow to red, depending on the nature of the crystalline and surface defects involved in the emission process. Although the nature of these defects is still under debate, it is widely admitted that reducing the size down to the nanoscale enhances the presence of the defects and the luminescence efficiency of ZnO nanostructures in the visible. We present a quick and convenient chemical solution approach to get unique mesospheric self-assembly hybrid ZnO system with intense photoluminescent quantum yield of 40-75 % and stable visible emissions. We develop luminescent layers of ZnO nanoparticles dispersed and embedded in a polymer matrix to be used as down-shifting materials in the structures of solar cells. Our luminescent ZnO layers are fabricated using an easy scale–up process, which is easily adaptable for industrial applications. We will also present the parameters influencing the luminescent efficiency of chemically synthesized ZnO nanoparticles used as down-shifting material. The issue of the optimization of the luminescence EQE, in conjunction with the nano- and mesostructure of the material will also be addressed. We will show how the chemical synthesis parameters influence the ZnO nanoparticle’s EQE and how they can be adjusted to reach EQE as high as 75 %. The possibility to disperse and embed the nanoparticles in polymers (for example PMMA) will also be discussed. Furthermore, the possibility of application of other ZnO nanostructures, namely zinc oxide nanowires, in gas sensors, is presented. These nanowires are fabricated by a simple and low-cost process - chemical bath deposition. They have similar luminescent properties as studied ZnO nanoparticles, i.e. they emit in the UV and in the visible spectral range, thanks to the defects and surface states. Their excitonic and visible emission is studied in the presence of gas vapors and the results demonstrate the change of the visible photoluminescence of ZnO nanowire array and that the material is able to adsorb gases. Finally, the mechanism of gas sensing is discussed