Fabrication and characterization of Cu2ZnSn(S, Se)4 with aluminum doping by spray pyrolysis followed by selenization

Spray pyrolysis is a simple way to fabricate CZTSSe and has potential for low-cost industrial manufacturing. Doping of elements can be easily conducted using spray pyrolysis by addition of dopant salts into solution. Aluminum doping in CZTSSe might be an alternative way to adjust bandgap for application to tandem cell or bandgap grading. In this paper, we demonstrate the Al-doing of CZTSSe by spray pyrolysis. Aluminum is introduced by adding AlCl₃·6H₂O into the precursor solution of CZTSSe. With aluminum in CZTSSe, the crystal structure remained kesterite, but c/a ratio is slightly changed. However, small grain layer was observed when aluminum was incorporated in this film, but this layer might be reduced by optimizing selenization condition.