Activity: Talks and presentations › Conference presentations
Kesterite solar cells based on pure sulfide CZTS (Cu2ZnSnS4) offer prospects of a cost effective and environmentally benign solution for photovoltaics. While promising on its own, CZTS is now receiving increased interest for applications in monolithic CZTS/Si tandem solar cells due to its high bandgap and low lattice mismatch with Si. However, integrating the Si and CZTS production steps to obtain an efficient monolithic cell is a challenging task. In this work, CZTS absorbers were produced by co- or sequential sputter deposition of the binary precursors SnS and ZnS and of the metallic precursor Cu. The characterization of a baseline single junction CZTS solar cell is presented, and some of the challenges and early results on the CZTS/Si tandem cell integration are reported. CZTS was grown on a Si substrate with a TiN diffusion barrier, to prevent the diffusion of some CZTS elements into Si during annealing – particularly Cu and S – that can degrade the photovoltaic properties of Si. The effects of annealing on the resulting structure were studied as a function of the initial CZTS precursor configuration and composition. The results of this initial integration and their implications for CZTS/Si tandem devices are discussed. The ideal thickness of the CZTS layer, in order to match the Si thickness for complete light absorption, was studied experimentally, in conjunction with optical simulations on complete CZTS/Si tandem structures.