Optimizing the optoelectronic properties of broadband FeS2/Si photodetectors via deposition temperature tuning in chemical bath deposition

This study investigates the fabrication and characterization of n-FeS2/p-Si heterojunction photodetectors using chemical bath deposition (CBD) at deposition temperatures ranging from 50 °C to 80 °C. The impact of temperature on the structural, morphological, and optical properties of FeS2 thin films was evaluated. X-ray diffraction (XRD) revealed polycrystalline cubic FeS2 with improved crystallinity as the deposition temperature increased. The optical energy gaps of the films ranged from 2.41 eV to 1.6 eV, decreasing with higher temperatures. Scanning electron microscopy (FE-SEM) showed that grain size increased from 30 nm to 180 nm as the temperature rose. Hall effect measurements confirmed the n-type conductivity of the film, with mobility decreasing from 5 to 3.17 cm2 V−1 s−1 at higher temperatures. The heterojunctions exhibited rectifying behavior, with the best ideality factor of 1.7 observed at 60 °C. The photodetector fabricated at 60 °C showed superior performance, with a responsivity of 0.37 A W−1 at 520 nm and 0.7 A W−1 at 770 nm, an external quantum efficiency of 52%, and a detectivity of 8 × 1011 Jones at 520 nm, making it the optimal configuration for efficient broadband photodetection.