Development of a new deposition procedure to growth Cu(In,Ga)Se2 thin film solar cells (M.Acciarri, S. Binetti, L. Miglio)

The strong need of reducing the PV related cost focused  the attention on thin film based devices. Such emerging technology in fact allows improving the efficiency to cost ratio, since the amount of material required for the realization of thin film solar cells is at least two order of magnitude lower than in the case of first generation PV devices. Among these second generation thin film devices the alloy Cu(In,Ga)Se2 (CIGS) is the most promising material due to the high efficiencies  recently obtained (20.1 % lab record).
A further reduction of CIGS solar cells cost could be achieved developing new easily scalable procedures not only on rigid but also on flexible substrates, this feature being really attractive for building integrated (BIPV) systems.
At MIB-SOLAR, a new and alternative approach for CIGS thin film growth has been tested in collaboration with a small enterprise, Voltasolar srl ( WWW.VOLTASOLAR.IT ). The growth method is different from the commercial ones (mainly based on co-evaporation processes) and consists of sputtering deposition of the metal elements combined with selenium evaporation, which allows deposition time of the CIGS layer lower than 15 min, matching the requirements for industrial applications. The cylindrical geometry of the deposition chamber can be exploited for a continuous process (i.e. roll-to-roll deposition) and different substrates can be used (11×14 cm2 soda lime glass, 120×14 cm2 stainless steel or 120×14 cm2 polyimide substrates).

Post-doctoral fellows: Jacopo Parravicini

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