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Department of Engineering, ICT and Technologies for Energy and Transport Patent Title Method for fabrŝĐĂƟŶŐ thin-Įlm solar cells. Ref. CNR 10335 Assignee(s): CNR CNR InsƟƚute: IMEM Main Inventor: Stefano Rampino Countries: IT Priority date: 26/05/2014 Abstract The ŝŶǀĞŶƟŽn allows to grow thin Įům solar cells by means of Pulsed Electron DeposŝƟŽn process (PED). This technique permits the reĂůŝnjĂƟŽn of solar cells with a net ƌĞĚƵĐƟŽn of the costs thanks to lower temperatures and excellent stoichiometric transfer of the material from the target to the substrate. These ideas are suitable for this process and provide a soluƟŽn of two ĐƌŝƟĐĂl issues: the uniformity of the deposŝƟŽn over large areas and the increase of the PED stability of the process over Ɵŵe. The Įƌst one is resolved through the opƟmizĂƟon of an array of PED sources arranged below a substrate moved convenientely. The second one can be overtaken by directly heĂƟŶŐ the substrate via the Joule eīect ;ůŝŵŝƟŶŐ dispersions and massive elements that usually reaches very high temperatures in the chamber heĂƟŶŐ all the walls and the device located inside). Background The CuInGaSe (CIGS) is reaching a great interest as material for photovoltaic ĂƉƉůŝĐĂƟon. Thanks to its high 2 ŽƉƟĐĂů absorpƟon coeĸcient, CIGS can absorb the totality of the solar light in a few microns thickness allowing to realize photovoltaic cells with ĞĸĐŝĞŶĐLJ values above 20%. However, the techniques used so far (co-evaporaƟon and spuƩĞƌing) require high substrate temperatures (500-600°C) and cause high waste of material on the walls of the deposŝƟŽn chamber. Technology Thanks to the typical features of the PED technique, the growth of the CIGS layer occurs preserving completely the stoichiometry of the target material even at low temperatures (300°C). However, the temperatures involved lead to a degradĂƟŽŶ of the performance of the source if maintained for long Ɵŵe and the deposiƟon from a single gun does not guarantee a high yield for the industrial ƉƌŽĚƵĐƟon. Advantages and ApplicaƟons The ideas developed in this patent arise from the need to insert the technique PED inside a ĐŽŶƟŶuous ƉƌŽĚƵĐƟŽn line of photovoltaic modules and allow both to maintain performance of the other sources for long periods thanks to the ŚĞĂƟŶŐ of the substrate only through Joule Ğīect both grow mini-modules 16x16cm thanks to a suitable arrangement of an array of sources PED. 2 Development stage Several solar cells have been grown by PED with eĸĐiency higher than 15% using a metal-coated soda-lime glass substrate heated by joule ĞīĞĐƚ͘ It is sƟůů in the ĐŽŵƉůĞƟŽn phase a vacuum chamber for the development of a pre-industrial ƉƌŽĚƵĐƟon system for CIGS solar cell based on the PED technique where the sources have been posŝƟŽŶĞd taking in account the results obtained thanks to the sŝŵƵůĂƟons presented in these studies. 29