Unraveling the photoconduction characteristics of single-step synthesized CuS and Cu₉S₅ micro-flowers

Owing to the alteration in the fundamental properties even by a slight variation in Cu/S ratio, the Cu–S system has been complicated and its role in photoconductive devices has been rarely investigated. Herein, CuS and Cu₉S₅ micro-flowers have been synthesized via a single-step solvothermal process and their photoconductors have been fabricated to unveil the optoelectronic characteristics. By increasing a Cu/S ratio from CuS to Cu₉S₅, the reduction in bandgap from 1.60 to 1.09 eV has been observed. In addition, the impact of bandgap on conductivity under dark and light has been investigated. Under Halogen light exposure, ~110 times increase in the photocurrent for Cu₉S₅ has been observed than CuS. The detectivity and responsivity of CuS and Cu₉S₅ were obtained to be 9.26 × 10⁵, 6.1 × 10⁶ Jones and 1.37 × 10⁻⁸, 1 × 10⁻⁶ A/W under Halogen light. In addition, the Cu₉S₅ photoconductor attained maximum responsivity, 2.5 × 10⁻⁴ A/W, and detectivity, 2.3 × 10¹⁰ Jones at 980 nm. More importantly, the photoconduction mechanism for CuS and Cu₉S₅ has been studied in-depth and the role of the Cu/S ratio on the photoconductivity has been evaluated.