Efficient optoelectronic properties of FeS2 nanostructures by Zn doping

In this study, un- and Zn-doped nanostructured pyrite (FeS2) films at different Zn concentrations were fabricated by the electrodeposition method. Photodetectors were fabricated with FTO/TiO2/un- and Zn-doped FeS2/Au configurations for optoelectronic applications. The effect of Zn concentration and TiO2 buffer layer on the efficiency of these devices was investigated through various characterizations. Optoelectronic characterizations showed that Zn doping increased photocurrent and conductivity in doped samples compared to the undoped ones. Calculating the ideality factor using the dark I-V curve revealed that Zn doping reduced the ideality factor in these devices, which indicates a reduction in the recombination rate and defects in doped samples. This finding was further confirmed by photoluminescence (PL) analysis. Moreover, the results of the space-chargelimited current (SCLC) model and Mutt-Gurney equation demonstrated that Zn doping enhanced carrier mobility. The elevated carrier concentration as a result of built-in field at TiO2/FeS2 heterojunction interface effectively separated the photogenerated carriers and increased the efficiency of the fabricated devices. The device with the lowest Zn doping concentration (a 9.2-fold increase in the responsivity compared to the undoped sample) showed the highest efficiency, so that the external quantum efficiency (EQE), photoresponsivity (R), and specific detectivity (D*) were obtained to be 48.16%, 206.30 mAW(-1), and 3.3x10(+9) (Jones), respectively, in the visible light spectrum.