ZnO nanowire-based radial heterostructures for photovoltaic applications

PhD grant from LABEX CEMAM - 2013-2016

In the field of solar cells, photovoltaicconversion is an attractive process to supply green and sustainable energy in amore and more critical environmental context. Photovoltaic companies have benefited over the last decade from asignificant growth, which is characterized by the predominant first and second generationsof solar cells made from bulk silicon and thin films with direct band gapsemiconductors such as CdTe, CdS or CIGS, respectively. However,the cost of solar cells must keep on decreasingwhile increasing its efficiency in order to make photovoltaic technologycompetitive.

In this context, the use of nanostructuredmaterials in the form of nanowires is very promising. By using a radialjunction surrounding  nanowires accordingto core shell heterostructures, light absorption (related to nanowire length) canbe separated from charge carrier collection (depending on nanowire diameter). Nanostructuredmaterials can therefore induce light trapping in nanowire ensemble, henceimproving absorption with respect to conventional planar layers. Furthermore, chargecarrier collection can be more efficient owing to the much smaller collection distanceand to the better crystalline quality of nanowires presenting a lower density ofdefects. It should be noted that nanostructured solar cells have a typicalthickness of several hundreds of nanometers, which is much smaller than thetypical thickness of several hundreds of micrometers for bulk silicon solar cells.Additionally, semiconductor heterostructures have been receiving an increasinginterest for fundamental aspects due to their valuable physical properties atnanoscale dimensions.

LMGP and SIMaP already have a strong background on the fabrication ofcore shell nanowire-based solar cells [1-4]. The present PhD thesis aims at designingand developing solar cells based on ZnO nanowires surrounding by an absorbing semiconductorshell, which is different from standard absorbing semiconductors such as CdTe,CdSe or CIGS. The PhD thesis willfocus on the selection of the absorbing semiconductor shell as well as on its growthby a chemical route and its structural ordering on ZnO nanowires. The study ofthe structural, electrical and optical properties of the resulting core shellZnO nanowires will be carried out by a wide variety of characterizationtechniques such as scanning and transmission electron microscopy, x-ray diffraction,spectrophotometry, Raman spectroscopy, photoluminescence and Hall effectmeasurements. Eventually, the fabrication of solar cells made from these heterostructureswill be performed in LMGP and will benefit from the collaboration withLEPMI-MOPS. Standard and refined electrical characterizations in terms ofphotovoltaic performances will be achieved thanks to the strong collaboration withIMEP-LAHC.

[1] V. Consonni, G. Rey, J.Bonaimé, N. Karst, B. Doisneau, H. Roussel et al., Appl. Phys. Lett. 98,111906 (2011).

[2] E. Puyoon G. Rey, E. Appert, V. Consonni et D. Bellet, J. Phys. Chem.C 116, 18117 (2012).

[3] S. Guillemin, V. Consonni, E. Appert, E. Puyoo, H. Roussel, and L.Rapenne, J. Phys. Chem. C 116, 25106 (2012)

[4] J.Michallon, M. Zanuccoli, A. Kaminski-Cachopo, V. Consonni et al., Mater.Sci. Eng. B 178, 665 (2013)

The PhD student will work in Laboratoiredes Matériaux et du Génie Physique (LMGP) and Laboratoire de Science etIngénierie des Matériaux et Procédés (SiMaP). Strong collaborations exist withother labs such as IMEP-LAHC, LEPMI, CEA-Grenoble or Institut Louis Néel.

Contact: Vincent Consonni

Lab websites:http://www.lmgp.grenoble-inp.fr and http://www.simap.grenoble-inp.fr

The applicant musthave an engineering school degree and/or a master of science in materialsscience and engineering, materials physics and chemistry or solid state physics.The applicant should be dynamic and highly motivated for the research work inlabs and should have human and English language skills. The interestedapplicants should send their resume and two or three references to EstelleAppert and Vincent Consonni.