Structural, optical and photoconductivity characteristics of manganese doped cadmium sulfide nanoparticles synthesized by co-precipitation method

Mn-doped CdS nanoparticles (NPs) have been synthesized by co-precipitation method and effect of Mn concentration on the structural, photoluminescence and photoconductivity properties have been studied. The X-ray diffraction (XRD) patterns show that the synthesized NPs have a cubical (zinc blende) phase. The clear lattice fringes in the high-resolution transmission electron microscopy (HRTEM) image, and selected area electron diffraction (SAED) patterns with bright circular rings with spots further confirms cubical nature. The estimated average particle size is found to be ∼3.1 nm by TEM image. UV–visible (UV–vis) absorption spectroscopy is used to calculate band-gap of material and blue shift in absorption peak indicates quantum size confinement effect. In photoconductivity study, variation of photocurrent with voltage on ln–ln scale is found to follow power law superlinearly due to injection of additional charge carriers from one of the electrodes. The growth and decay in photocurrent spectra exhibit anomalous behaviors which may be attributed to photo-induced chemisorptions of oxygen molecules on surface of NPs. A significant improvement in photocurrent has been observed in Mn-doped CdS NPs with concentration of Mn as 3 mol% as compared to un-doped CdS NPs. Photoluminescence (PL) spectra of un-doped as well as Mn-doped CdS NPs have one emission peak centered at ∼526 nm whereas Mn-doped CdS NPs show one additional emission peak centered at ∼575 nm which may be assigned to 4T1 → 6A1 transitions of Mn2+.

► This paper reports the structural, photoluminescence and photoconductivity properties of manganese doped cadmium sulfide nanoparticles for different doping levels (0%, 1%, 3% and 5 mol%).
► It has been observed that doping level of Mn (3 mol%) highly enhances the photoconductivity.
► Both un-doped as well Mn-doped CdS NPs are found to exhibit an anomalous photoconductivity which is attributed to photo-induced chemisorptions of oxygen molecules on surface of NPs has been discussed.
► The proposed work suggests very promising application as a photoresistor, photodetector, etc.