Inhibiting aluminum oxidation in CuInAl precursor films: Significance for achieving high-performance Cu(InAl)Se₂ solar cells

In this work, we demonstrate the effects of aluminum and aluminum oxide within CuInAl precursor films on the formation process of Cu(InAl)Se2 (CIASe) thin films. We carried out a large number of experiments to optimize the conditions for obtaining CIASe thin films with excellent adhesion and electrical properties. Our findings suggest that the fabrication conditions of the precursor films, such as the vacuum level of sputtering chamber and the structure of the precursor films, significantly affect to the growth of the CIASe layer during selenization annealing. Through a series of experiments, we successfully obtained a 2.4 mu m-thick CIASe thin film with strong adhesion to the Mo-coated substrate and fabricated a CIASe solar cell with an efficiency of 7.7%. Our study demonstrates the great potential of the two-step fabrication approach for CIASe thin film production, and further improvements are expected by optimizing the fabrication conditions.