Suppression of CuS phases in CuInS2 electrodeposition and sulfurization with heat treatment

CuInS2 films are promising for future solar cell technology. However, the formation of the CuS phase during the growth of CuInS2 thin films may hinder the performance of the CuInS2-based solar cell. Therefore, the removal of the excessive CuS phase is required during fabrication of CuInS2 films. In this research, we fabricated a CuInS2 film using Cu–In electrodeposition and a sulfurization process. Electrodeposition tests were conducted in solutions of various pH values and deposition voltages to grow high-quality precursor films. Moreover, to suppress formation of the CuS phases, heat treatment was incorporated in the fabrication process. We found that an appropriate amount of sulfur powder and a suitable heat treatment temperature could suppress the CuS phases and form well-crystallized CuInS2. Improvements in film quality and removal of the CuS phase can be confirmed by X-ray diffraction scanning electron microscope imaging, and energy dispersive spectrometer measurements. High-quality film with superior crystalline structure and surface morphology was formed with sulfurization and heat treatment at 600 °C.

► CuInS2 films were fabricated by Cu–In electrodeposition and sulfurization.
► Electrodeposition with various pH values and deposition voltages was conducted.
► Heat treatment was used to suppress formation of the CuS phase.
► An appropriate amount of sulfur powder was important to suppress the CuS phase.