Fabrication of Cu2ZnSn(S,Se)4 absorber films by selenization of different Cu2ZnSnS4 nanocrystal coatings

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) has been identified as one of the most promising thin film solar cell absorber candidates composed of earth-abundant elements. We demonstrate here an environmentally friendly and scalable solution-based approach to fabricating CZTSSe absorber films with Cu2ZnSnS4 (CZTS) nanocrystals by a selenization process. In this facile approach, phase pure and single crystal CZTS powders were synthesized with the method of molten salt reactions and dissolved in the nontoxic solution of ethanol and ethyl cellulose, forming a stable ink for depositing precursor films. It was found that the initial ink composition plays an important role in determining the properties of CZTSSe absorber films. All synthesized powders and films were analyzed with respect to their phase component, microstructure and chemical composition. The optoelectronic properties of CZTSSe absorber films investigated by UV-VIS spectrophotometer and Hall effect measurement can well meet the requirements for utilization in thin film solar cells, illustrating that the demonstrated approach has broad application prospects for CZTSSe solar cell production.