Cu2ZnSnS4 thin film solar cells with 5.8% conversion efficiency obtained by a facile spray pyrolysis technique

Abstract

An attempt was made to fabricate Cu₂ZnSnS₄ (CZTS) thin film absorber on a Mo-coated glass substrate by using facile spray pyrolysis deposition of a precursor film from an aqueous solution containing Cu(NO₃)₂, Zn(NO₃)₂, Sn(CH₃SO₃)₂ and thiourea. In order to obtain a stable solution for the spray pyrolysis deposition without formation of an SnO₂ precipitate, the mixing order of source materials was found to be important. Annealing of the thus-obtained precursor film in sulfur vapor at temperatures ranging from 580 °C to 600 °C resulted in successful formation of homogeneous films composed of CZTS crystallites. Based on structural analyses of CZTS films having different Sn contents, an Sn-rich composition compared to its stoichiometric amount was found to be essential for efficient grain growth of the resulting CZTS films. A solar cell based on the Sn-rich CZTS film obtained by an optimum annealing condition exhibited maximum conversion efficiency of 5.8%.