Interface Defects in GIGS-based Solar Cells from Coupled Electrical and Chemical Points of View
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MRS proceeding
Canava et al.
Symposium H
Interface Defects in GIGS-based Solar Cells from Coupled Electrical and Chemical Points of View B. Canava1, J. Vigneron1, A. Etcheberry1, S. Ould Saad2, Z. Djebbour2, D. Mencaraglia2, J.F. Guillemoles3 and D. Lincot3 1 Institut Lavoisier (IREM, UMR 8637 CNRS) Université de Versailles-Saint Quentin, 45 ave des Etats Unis, 78035 Versailles Cedex, France 2 Laboratoire de Génie Electrique de Paris (LGEP, UMR 8507 CNRS) LGEP-Supélec, Plateau de Moulon, 91192 Gif-sur-Yvette Cedex, France 3 Laboratoire d’Électrochimie (LECA, UMR 7575 CNRS) Ecole Nationale Supérieure de Chimie de Paris, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France ABSTRACT Chemistry of co-evaporated CIGS surfaces submitted to chemical treatments relevant to fabrication steps were investigated by XPS and admittance spectroscopy. A Se XPS signal specific of the CIGS surfaces was identified. Surface states seen by Admittance and surface chemistry are seen to change significantly during the elaboration steps. Consequences for device elaboration are briefly discussed.
INTRODUCTION CuInGaSe2 provides today the most efficient way for thin film photovoltaic devices, as shown by its remarkable performance in laboratory-sized cells, and more significantly on large area [1]. Yet, one of the main challenges to progress in that technology rests with the control of interfacial properties. This problem is common to many semiconductor devices, and is specialy crucial in heterojunction devices. Due to the chemical complexity of the interface in devices, the causes for the high performance of the devices or the performance degradation are not yet well understood. In the present work we aimed at finding relationships between electrical and chemical properties of the CIGS/buffer/ZnO interface in CIGS based solar cells. In this perspective, we have investigated interfaces by and admittance spectroscopy. Co-evaporated CIGS samples of technologically relevant elaboration underwent various surface treatments, analog to those possibly involved in fabrication steps (aging in humid air, NH3 diping, ...) before their high resolution XPS study. ZnO window completed devices were then characterized by admittance. Admittance measurements have been proposed as a powerful method for the identification of bulk and interface traps in semiconductor devices. For thin film devices we have extensively used this technique to investigate the gap states spectroscopy of hydrogenated amorphous silicon and related materials [2-5]. In this paper, this technique was performed to study CIGS solar cells using a method proposed by Walter et al. [6] to derive the gap states distribution from the capacitance spectra.
H5.2.1
MRS proceeding
Canava et al.
Symposium H
EXPERIMENTAL The CIGS thin films (thickness about 2 µm) were prepared by co-evaporation of the elements on Mo-coated glass (thickness about 0.5 µm) at the Zentrum fur Solarenergie und Wasserstoff, Stuttgart as described in [1]. Their nominal composition was: Cu 21.5%, In 17.9%, Ga 8.8%
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