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 μm-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. Development progress of aluminum oxide layer within CIASe thin films. [Display omitted] •The effects of the structure of CuInAl precursor films and aluminum oxidation were investigated.•Aluminum oxide could not be selenized, resulting in the delamination and exfoliation of CIASe thin films.•The deposition position of aluminum in the precursor films greatly affects the development of CIASe.•Aluminum oxidation has been inhibited by modifying the precursor film structure and adjusting the sputtering vacuum level.•By inhibiting aluminum oxidation, a CIASe solar cell with an efficiency of 7.7% has been achieved.