Role of Cobalt Doping in CdS Quantum Dots for Potential Application in Thin Film Optoelectronic Devices

Abstract

Colloidal quantum dots (QDs) are promising materials for optoelectronic devices. In this paper, monodispersed and environment stable cobalt (Co)-doped CdS QDs have been synthesized and characterized for potential application in thin film optoelectronic devices. The Rietveld refinement profiles of X-ray diffraction data reveal that both undoped and Co-doped CdS QDs exhibit a zinc blende structure without any impurity phase. X-ray photoemission spectroscopy has been used for electronic structure and valence state analysis. The detailed information about the doping, coordination number, and local geometry has been studied with XANES and EXAFS measurements. Analysis of Raman spectra reveals that the intensity of longitudinal optical (LO) modes varies considerably due to short-range structural disorder. Absorption spectra also show the creation of a new doping band (DB) near the NIR region in Co-doped CdS QDs which is not observed for doping of many other transition metals. The width of this DB increases with an increase in the doping concentration, and enhancement of photoconductivity of the thin film heterojunction of the samples has been obtained. Evolution of the new DB and enhancement of the photocurrent upon Co doping make the prepared quantum dots very promising materials to exploit for fabricating UV–vis/NIR thin film optoelectronic devices.

Enhanced Photoresponse and Wavelength Selectivity by SILAR-Coated Quantum Dots on Two-Dimensional WSe2 Crystals

“…Figure d shows the Raman spectra of the CdS, CdSe, and PbS NPs, measured by a 532 nm laser excitation source at room temperature. For the CdS NPs coated on the WSe 2 sample, the spectrum exhibits intense peaks at 294 and 515 cm –1 that can be assigned to the longitudinal optical (LO) phonon mode and its overtone (2LO), respectively . In the case of CdSe NPs coated on the WSe 2 sample, the peaks occur at 200 cm –1 (1LO) and 406 cm –1 (2LO) .…”

Investigation of Ag doping and ligand engineering on green synthesized CdS quantum dots for tuning their optical properties

“…The Co-doped CdS QDs were successfully synthesized through a chemical route using 1-monothioglycerol as a capping agent. The optoelectronic properties can be tuned with the variation in the Co doping [24]. Ag-doped CdS nanostructure was synthesized through the coprecipitation method and found the reduction in band gap upon Ag doping in comparison to CdS QDs.…”

Highly Sensitive Broadband Photodetector Based on PbI2-Passivated CdS:Mn Quantum Dots with a Spectrally Flat Response

“…On the other hand, due to their wider band gap nature, the spectral response range of these devices is relatively narrower than that of Pb-based QD devices. This spectral response of Cd-based QDs has been enhanced significantly by metal doping. − However, uniformity of the spectral photoresponse of these devices is very poor and needs further research for practical applications. ,, …”

“…19−21 However, uniformity of the spectral photoresponse of these devices is very poor and needs further research for practical applications. 8,21,22 In addition to spectral broadening and uniformity for developing nanocrystal-based broadband photodetectors, it is also important to improve charge transport through the QDs. Colloidal QDs are commonly surrounded by long-chain organic molecules, which are required for the uniform growth of QDs.…”