Preparation of highly electroactive cobalt sulfide coreshell nanosheets as counter electrodes for CdZnSSe nanostructure-sensitized solar cells

摘要

A facile method for the synthesis of Co_3S_4 coreshell hexagonal nanosheets (NSs) from Co(NO_3)_2 and thioacetamide under alkaline conditions in the presence of poly(vinylpyrrolidone) has been demonstrated. At the molar ratios of thioacetamide/Co~2 of 0.26, 0.52, and 2.6, we prepared hollow-, semi-hollow, and non-hollow Co_3S _4 coreshell hexagonal NSs. We have found that Ostwald ripening occurring at the core/shell interface accounts for the formation of the hollow Co_3S_4 coreshell NSs, each consisting of a core of 80±30 nm in diameter and a shell of 25±5 nm in thickness. Three CdZnSSe nanostructure-sensitized solar cells incorporating Co_3S _4 NSs provide an average power conversion efficiency of 3.7±0.1, showing high electrocatalytic activity of the Co _3S_4 NSs toward polysulfide electrolyte.