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

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 degrees C to 600 degrees 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%.