Description of the proposed research work

Transcription

1 Supervisors: Prof. Bruno Masenelli and Dr Alexandra Apostoluk (Associate Professor) Laboratory: Lyon Institute of Nanotechnologies, INL, UMR CNRS Description of the proposed research work Fabrication, structural and spectroscopic studies of wide bandgap semiconducting nanoparticles of SiC and ZnO for application as light converters in solar cells Abstract: The proposed subject concerns the fabrication and characterization of high bandgap semiconducting nanoparticles of SiC and ZnO by means of optical spectroscopy and their application in the luminescent down-shifting layers in solar cells in order to increase the solar cell's efficiency. We are able to control the stoichiometry and crystallinity of SiC and ZnO nanoparticles so that the desired emission features (high blue emission for SiC and high green-red light emission from ZnO) under UV illumination are obtained. The ZnO and SiC nanoparticles will be characterized structurally by means of transmission electronic microscopy (TEM), Rutherford Back Scattering (RBS) and by X-ray diffraction (XRD). The optical properties (absorption, emission) will be probed by absorption spectroscopy, ellipsometry, the UV-excited photoluminescence, cathodoluminescence and time-resolved photoluminescence. The studied ZnO and SiC nanoparticles will be put together in a matrix and deposited on the top of a solar cell, in order to take advantage of the luminescence of SiC and ZnO which convert the UV light (which is not efficiently used by a solar cells for the photovoltaic conversion) into blue, green and red light, where the solar cell is more efficient, thus increasing the overall solar cell's efficiency. In recent years, the development of photovoltaics (PV) has been concentrated on activities aimed at reducing the manufacturing costs of PV devices, as well as at the improvement of their photovoltaic conversion efficiency. Adjusting both of these factors at the suitable level is still easily realizable in the field of thin film solar cells, which can make them competitive for the conventional energy sources. This requires, however, the elaboration of appropriate and easy-to-implement fabrication technologies, as well as providing relatively high efficiencies of commercialized devices. One of the concepts permitting to increase the efficiency of solar cells without any modification of their fabrication process is adding on their top a thin layer permitting to convert the UV light into visible light. Such a phenomenon is called downshifting. In this study we propose the application of a film of SiC and ZnO nanoparticles as a downshifting layer placed on the front side of a solar cell (SC), in order to generate a low-energy photon for every incident high-energy photon for enhancing its external quantum efficiencies and the conversion efficiency. Optical down-shifting by nanoparticles (NPs) enhances the SCs efficiency by converting the UV sunlight into visible light, which is used more effectively by the SC as its quantum efficiency is lower in the UV region than in the VIS spectral zone due to front surface recombination of hot photocarriers. As ZnO NPs convert UV light to green and red, the conversion of the UV light into the blue light has to be done by another type of nanoparticles and it turns out thus SiC emits efficiently in the blue spectral zone. Thus mixing the SiC and ZnO nanoparticles in the same luminescent down-shifting layer (LDSL) deposited on the top of a solar cell, we assure an efficient conversion of the UV light into the whole visible spectrum: blue, green and red light, where the solar cell s efficiency is higher. 1

2 More precisely, the short wavelength response of a solar cell, such as CIGS, CdTe or amorphous silicon SC, can be improved by the application of a LDSL to the SC structure. We propose the use of the LDSL containing both SiC and ZnO NPs able to absorb UV light (λ < 390 nm), where the SC s spectral response (SR) is low (due to larger absorption of high energy photons in the surface region), and re-emitting at longer wavelengths (λ > 400 nm), where the SC s SR increases. The nanoparticles will be excited by a UV light, giving rise to the visible photoluminescent signal. The origin of this visible luminescence in metal oxides like ZnO is still controversial, though it is widely admitted that the oxygen vacancies are at its origin 1. Thus we propose to augment green and red luminescence of zinc oxide nanoparticles by deliberate introduction of oxygen and other defects in their structure thanks to the control of their stoichiometry and doping and to use their visible luminescence to enhance solar cells efficiency. The stoichiometry, crystallinity and surface quality of the studied NPs can be adjusted via the control of the NPs synthesis parameters, which permits to obtain the highest visible photoluminescence emission, necessary for the efficient down-shifting. It is expected that the introduction of an appropriate NPs layer onto a thin film solar cell, as it is schematically depicted in Fig.1, causes the increase of the external quantum efficiency and in this way, the increase of the overall conversion efficiency of a PV device. Fig.1. Schematic presentation of a down-shifting layer, placed on top of a pre-existing single junction solar cell the proposed structure. The optimization of the parameters of the LDSL (thickness of the matrix layer, concentration of the Si Cans ZnO nanoparticles in the matrix, transparency, etc.) will be performed using SCAPS program 2. Both supervisors of this work have already performed preliminary investigations 3,4,5,6,7,8 which showed that ZnO NPs have a great potential when applied as a down-shifting layer 1 A. Janotti and C. G. Van de Walle, Fundamentals of zinc oxide as a semiconductor, Rep. Prog. Phys. 72, , A. Apostoluk, Y. Zhu, B. Masenelli, D. Hapiuk, B. Canut, A. Focsa, J.-J. Delaunay, M. Sibiński, K. Znajdek, Z. Lisik, ZnO nanoparticles for solar cell applications, the European workshop on Transparent Conductive Materials (TCMs), Grenoble, France, 14th 15th June A. Apostoluk, B. Masenelli, D. Hapiuk, B. Canut, Y. Zhu, J.-J. Delaunay, M. Sibiński, K. Znajdek, Z. Lisik, Optical and electrical properties of ZnO nanoparticles fabricated by advanced physical methods for downshifting applications, IwZnO The 7th International Workshop on Zinc Oxide and Related Materials, Nice, France, 11th-14th September

3 generating low-energy photons out of high-energy incident photons which allows enhancing the solar cell quantum efficiency. Cooperation in this subject of the teams from Institut National des Sciences Appliquées de Lyon (INSA Lyon, France), Lodz University of Technology (Lodz, Poland) and Tokyo University (Todai, Tokyo, Japan) has been performed in the frame of two bilateral projects granted within the Polish-French Polonium program, the last one coming to an end on 31 st December The student will profit from a widely recognised expertise in nanoparticle fabrication techniques and optical spectroscopy of nanostructures of the INL as both of the thesis supervisors work on a full time basis in this domain. The student will also closely collaborate on the physical and optical characterisation of ZnO nanoparticles with the team of Prof. Stéphane Danièle from Institute de Recherches sur la Catalyse et l Environnement de Lyon (IRCELyon), an expert on the chemical synthesis of ZnO nanoparticles. The international collaboration with the laboratory of Prof. Znigniew Lisik from Lodz University of Technology (Lodz, Poland) and Prof. Jean-Jacques Delaunay from the University of Tokyo School of Engineering (Todai, Tokyo, Japan) will also support this research topic. Thesis director: Prof. Bruno Masenelli Number of papers in the reviewed international journals: 47 Number of citations: 750 H-factor: 17 Academic qualifications: 1995 Master engineer s degree from the Ecole Centrale de Lyon (one of the top level engineer schools in France) researcher at the CEA (French institute of nuclear energy) PhD in condensed matter physics from the Ecole Centrale de Lyon. Previous academic positions held: a post doc in Pr. Zuppiroli s group at the EPFL (Switzerland) associate professor at the Laboratoire de Physique de la Matière Condensée at the University Claude Bernard Lyon 1, Lyon, France. 5 A. Apostoluk, Y. Zhu, B. Masenelli, J.-J. Delaunay, M. Sibiński, K. Znajdek, A. Focsa, Improvement of silicon solar cell quantum efficiency by ZnO nanoparticles down shifting effect, Microtherm 2013 conference, Lodz, Poland, 25th-28th June A. Apostoluk, Y. Zhu, B. Canut, B. Masenelli, J.-J. Delaunay, K. Znajdek, M. Sibiński,. Investigation of luminescent properties of ZnO nanoparticles for their use as a down-shifting layer on solar cells, Phys. Status Solidi C 10 (10), , 2013; DOI: /pssc Y. Zhu, A. Apostoluk,, L. Shibin, S. Daniele, B. Masenelli, ZnO nanoparticles as a luminescent down-shifting layer for photosensitive devices, J. Semicond. 34 (5), (6 pp), 2013; DOI: / /34/5/053005, 8 A. Apostoluk, Y. Zhu, B. Masenelli, J.-J. Delaunay, M. Sibiński, K. Znajdek, A. Focsa, I. Kaliszewska, Improvement of the solar cell efficiency by the ZnO nanoparticle layer via the down-shifting effect, Microelectronic Engineering 127, 51-56, 2014; DOI: /j.mee

4 Present academic position: Since 1 st September 2010 full professor at the Institute of Applied Sciences of Lyon, France, and researcher at Lyon Institute of Nanotechnologies (INL UMR CNRS 5270). Research focus: His expertise field is the synthesis and characterization (optical and structural) of clusters and nanoparticles and nanowires, especially ZnO, MgO, SnO 2. He is the leader of the Spectroscopy and Nanomaterials team at the Institute of Nanotechnologies of Lyon (INL, UMR CNRS 5270). He works on optical spectroscopy and imaging (SEM, TEM, EDX), photoluminescence, single particle spectroscopy, time resolved spectroscopy, cathodoluminescence and nanocathodoluminescence. Selected publications in recent five years: 1. Competition between exciton phonon interaction and defects states in the 3.31 ev band in ZnO, D. Tainoff, B. Masenelli, P. Mélinon, A. Belsky, G. Ledoux, D. Amans, C. Dujardin, N. Fedorov, P. Martin, Phys. Rev. B 81, (2010). 2. ZnO dense nanowire array on a film structure in a single crystal domain texture for optical and photoelectrochemical applications, M. Zhong, Y. Sato, M. Kurniawan, A. Apostoluk, B. Masenelli, E. Maeda, Y. Ikuhara, J. Delaunay, Nanotechnology 23, (2012). 3. p doping in expanded phases of ZnO : an ab initio study, D. Hapiuk, M. Marques, P. Melinon, J. Flores-Livas, S. Botti, B. Masenelli, Physical Review Letters 108, (2012). 4. ZnO nanoparticles as a luminescent down-shifting layer for photosensitive devices, Y. Zhu, A. Apostoluk, S. Liu, S. Daniele, B. Masenelli, Journal of Semiconductors 34, (2013). 5. Oriented Attachment of ZnO Nanocrystals, D. Hapiuk, B. Masenelli, K. Masenelli-Varlot, D. Tainoff, O. Boisron, C. Albin, P. Melinon, Journal of Physics and Chemistry C: Nanomaterials and Interfaces 117, (2013). 6. Extended-Defect-Related Photoluminescence Line at 3.33 ev in Nanostructured ZnO Thin Films, S. Guillemin, V. Consonni, B. Masenelli, G. Bremond, Applied Physics Letters 6-11, (2013). 7. Investigation of luminescent properties of ZnO nanoparticles for their use as a downshifting layer on solar cells, A. Apostoluk, Y. Zhu, B. Canut, B. Masenelli, J. Delaunay, K. Znajdek, M. Sibinski, Physica Status Solidi (c): Current Topics in Solid State Physics 10 (10), 1301 (2013) 8. Improvement of the solar cell efficiency by the ZnO nanoparticle layer via the downshifting effect, A. Apostoluk, Y. Zhu, B. Masenelli, J. Delaunay, M. Sibinski, K. Znajdek, A. Focsa, I. Kaliszewska, Microelectronic Engineering (2014) pp (2014), 9. Thermodynamics of Nanoparticles: Experimental Protocol Based on a Comprehensive Ginzburg-Landau Interpretation, D. Machon, L. Piot, D. Hapiuk, B. Masenelli, F. Demoisson, R. Piolet, M. Ariane, S. Mishra, S. Daniele, M. Hosni, N. Jouini, S. Farhat, P. Melinon, NanoLetters 14, (2014). Thesis co-director: Dr Alexandra Apostoluk, Associate Professor at INSA Lyon and INL Dr Alexandra Apostoluk, aged 39, has been working on the emission of polymer and inorganic materials since her Engineering and MSc at Wroclaw University of Technology (Poland) and through her PhD in at Université d Angers. In 2003, she joined the Commissariat à l Energie Atomique (CEA) in Saclay for a 2-year post-doc on polymer semiconductors. In 2005 she worked as a lecturer and researcher at the University of Technology of Troyes. In 2006 she became an associate professor at INSA Lyon, working on III-V and II-VI nanostructures. She has a rich experience in both national and international 4

5 academic and industrial research projects or networks and educational projects (ANR, European FP6, Egide project Osmosis and Polonium, French GDR, Tempus) and participated in 3 ANR projects. She is a co-author more than 21 scientific papers (h index 7) and was 5 times an invited speaker in international conferences. She worked as an invited researcher at Thamassat University (Bangkok, Thailand), KEIO University (Yokohama, Japan) and currently at Tokyo University (since 1 st February 2015 till 1 st May 2015). Thanks to her training and thematic and geographic mobility (Poland, France, Thailand, Japan), she acquired a polyvalent expertise in the nanomaterial fabrication and deposition techniques, structural properties of polymer and crystalline materials, electrical and optical properties of metallic oxides and in the field of optical spectroscopy and time resolved spectroscopy. 5