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

Abstract

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.