Visible light-assisted instability of kesterite Cu₂ZnSnS₄: What are the implications?

The development of efficient photovoltaic devices utilizing durable and cost-effective materials such as CZTS and similar ones represents a big challenge. Here, the comparison of thermodynamic calculations and electrochemical experiments reveals detrimental degradation of CZTS regardless of pH values and potentials applied. Cathodic polarization yields to the full decomposition of CZTS, while anodic polarization stabilizes partly CZTS by passivation of its surface with less-active phases. The presence of water, in general, provokes the decomposition of CZTS to various undesired phases which most likely affect the device parameters. The possible mechanism for the degradation of CZTS is proposed considering its electronic structure. Certain similarities on unfavorable processes occurring with analogous materials are expected.