Cu2ZnSn(S,Se)4 (CZTSSe) solar cells

Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have gained recent research attention as lab-scale devices have achieved 12.6% power conversion efficiency (p.c.e.) [1]. However, CZTSSe performance is limited by low open-circuit voltages (VOC) which can be associated withthe detrimental defect properties of the bulk absorber [2]. One route to improve device performance of CZTSSe absorbers is through material alloying, where various elements can be incorporated into the tetragonal crystal lattice to modify the optoelectronic properties of the absorber. Notably, Ge-alloyed Cu2Zn(Sn,Ge)(S,Se)4 (CZTGeSSe) has demonstrated improved performance for CZTSSe absorbers through improved optoelectronic properties and the ability for band gap tuning/grading of the film [3]. In this work, we further expand our research in kesterite-based alloy material systems to include Ag-alloyed (Ag,Cu)2ZnSnSe4 (ACZTSe),where modification of the absorber properties has similarly been achieved. Here we report the successful formation of ACZTSe solar cells from heterogeneous nanocrystal inks and characterize the role of Ag on the grain-growth, absorption, defect, and device properties of this material. Nominal atomic Ag-alloy concentrations of [Ag]/([Ag]þ[Cu]) at 0%, 5%, and 50% are considered here