Lithium-doped Cu₂ZnSnS₄ superstrate solar cells with 5% efficiency – An alternative to thin film kesterite photovoltaics

Cu₂ZnSnS₄ or kesterite was branded as “the dark horse of next-generation solar energy conversion” in a recent viewpoint article due to its advantageous inorganic, earth abundant, non-toxic composition over perovskites. It was also pointed out that an alternative device structure to thin-film configuration could be a key to unlock the full potential of kesterite photovoltaics. In response to this need herein a Cu₂ZnSnS₄ @TiO₂ superstrate solar cell built via ethanol solution processing is described characterized by record efficiency of 5% and excellent stability. More specifically, lithium doping was found to promote kesterite grain growth and minimize interface charge recombination opening new prospects for kesterite photovoltaics.