Fabrication of In₂S₃ and In–Ga–S Thin Films via Atmosphere‐Controlled Fine‐Channel Mist Chemical Vapor Deposition

In the field of thin‐film solar cells, there is a growing need for cadmium‐free buffer layers and fabrication techniques that are both cost‐effective and environmentally friendly. In this study, the deposition of In₂S₃ and In–Ga–S thin films as alternative buffer layer materials in thin‐film solar cells, using mist chemical vapor deposition (CVD) at atmospheric pressure, is focused on. Indium diethyldithiocarbamate (DTC) and gallium DTC dissolved in dehydrated tetrahydrofuran are used as precursors. The deposited In₂S₃ demonstrates a wider direct bandgap (E_g‐dir ≈ 2.7 eV) than CdS, showing a potential for reducing parasitic absorption. Introducing a certain amount of gallium into In₂S₃ induces structural changes, resulting in a wider bandgap material. This bandgap widening primarily lowers electron affinity, making it beneficial for absorber materials with wider bandgap energies. Overall, the In₂S₃ and In–Ga–S thin films deposited via mist CVD exhibit preferable properties as alternatives to the CdS buffer layer. Moreover, the deposition technique proposed in this study can be adapted for the nonvacuum and cost‐effective deposition of other sulfide materials.