Cu/(Co+Sn) ratio effects on physical and photodetective properties for visible light absorbing Cu2CoSnS4 nanoparticles via a one-pot hydrothermal process

Abstract

The composition ratio plays a vital role in modulating the thermal, magnetic, and optoelectronic properties of earth-abundant quaternary chalcogenides. Here we report on an impact of Cu/(Co + Sn) ratio on secondary phase formation, size, and shape of Cu2CoSnS4 (CCTS) nanoparticles synthesized via monoethanolamine (MEA) promoted the hydrothermal process. The CCTS phase formation mechanism is experimentally elucidated by a time-dependent synthesis study during a one-pot facile hydrothermal reaction, and it is confirmed by using X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analysis. The morphology, particle size distribution, and shape of synthesized nanoparticles are examined by field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) analysis. The N-Methyl-2-pyrrolidone (NMP) solvent-based CCTS paste was drop-casted on a thermally oxidized silicon wafer (∼100 nm SiO2) to form films. The increase in optical bandgap from 1.48 eV to 2.00 eV is observed for an increase in Cu/(Co + Sn)) ratio of prepared CCTS films. The electrical, photodetection properties of the prepared films with respect to the (Cu/(Co + Sn)) ratio under dark and light illumination are studied. The lowest sheet resistance (Rsh= (13.56 ± 0.9) × 103 Ω/cm) and contact resistance (Rc= (108.31 ± 3.43) × 103 Ω) is obtained for devices made with a higher value of Cu/(Co + Sn) ratio = 1.17. On the other hand, the highest photosensitivity (Sph = 32%), photoresponsivity (Rph = 75.58 mA/W), and detectivity (Dph = 1.44 × 108 Jones) are demonstrated for device assembled with the lowest ratio (∼0.86) of Cu/(Co + Sn). The present study reveals that Cu/(Co + Sn) ratio affects a significant impact on such as a phase, morphology, chemical compositional ratio of nanoparticles, optical, electrical, and photoresponsive properties of prepared films.