Colloidal synthesis of high-quality Cu2MnSnS4 nanocrystals: structural, morphological, and optoelectronic investigation for applications in thin-film solar cells

Abstract

Colloidal semiconductor nanocrystal solar cells have been extensively developed in recent years and achieved a power conversion efficiency of ~ 15%. However, cost, toxic constituent elements, and pure-phase materials synthesis are major concerns for large-scale commercialization. Here in this report, we have successfully synthesized pure-phase crystalline Cu₂MnSnS₄ nanocrystals using the hot injection method which is further carefully characterized by various state-of-the-art techniques to investigate its structural, morphological, and optoelectronic properties. The high optical absorption and optimal band gap of 1.1 eV are observed, which is highly suited for solar cell applications. Furthermore, we pioneered the idea of fabricating the Cu₂MnSnS₄ nanocrystal-sensitized solar cell. We achieved a notable power conversion efficiency of 1.1% (~ fourfold higher) with n-CdS buffer layer than w/o n-CdS, 0.3%. The enhanced efficiency is directly attributed to the improved charge transfer and retard charge recombination across the p-Cu₂MnSnS₄/n-CdS interface. So far, to the best of our knowledge, we report the highest power conversion efficiency of 1.1% for Cu₂MnSnS₄ nanocrystals sensitized solar cell and energy band diagram for understanding the mechanism. The results were validated using an energy band diagram constructed using the cyclic voltammetry technique.