Cadmium sulfide (CdS) nanoparticles were synthesized by simple and low cost homemade hot injection method at low process temperature using different sulphur sources. The effects of sulphur concentration on the structural, morphological, and optoelectronic properties of synthesized CdS films were studied using a range of characterization techniques: X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and UV-Visible spectroscopy. The XRD studies revealed the formation of hexagonal type CdS nanoparticles. The varying morphology dependence on the sulphur source was ascertained from FESEM analysis. The longitudinal optical (LO) phonon vibrational modes of CdS were assigned in Raman spectra at 300 and 600 cm-1. The band gap of the CdS particles was estimated to be 2.30 eV from Tauc's plots. Consistent with the experimental results, our first-principles DFT calculations predict the band gap of CdS nanoparticles to increase with decreasing S concentration: Cd 52 S 52 (2.38 eV) Cd 52 S 51 (2.52 eV) and Cd 52 S 50 (2.65 eV), with both the valence and conduction band edges demonstrated to be dominated by S-p states.
Inorganic metal halide perovskites CsPbX3 (X = Cl, Br, and I) has achieved extensive attention in recent years for photovoltaics because of their unique properties like tunable band gap, high charge carrier mobility, high absorption coefficient, etc. and which makes it suitable for optoelectronic applications. In this work, we have reported a facile synthesis method of inorganic CsPbBr3 nanoparticles (NPs) at room temperature using cesium bromide (CsBr) as a Cs source, lead bromide (PbBr2) as Br source, oleic acid, and Oleylamine as capping ligands. Nucleation starts immediately after the injection of a precursor solution into the toluene. Synthesis of CsPbBr3 NPs was confirmed by X-Ray diffraction pattern, UV-Visible spectroscopy, photoluminescence (PL), scanning electron microscopy (SEM), and atomic force microscopy (AFM). X-ray diffraction pattern reveals mainly the monoclinic crystal structure of CsPbBr3 NPs. The UV-Vis absorption spectra and PL spectra show a strong absorption peak at 509 nm, emission peak at 505 nm, and the band gap of CsPbBr3 to be 2.2 eV. The synthesized CsPbBr3 exhibit regular cuboid like structure with a particle size of approximately 400-500 nm. The surface roughness morphology of CsPbBr3 NPs was studied using AFM, and it shows the roughness of the CsPbBr3 films was around 260 nm. These results provide a facile synthesis method, and CsPbBr3 NPs are a suitable candidate for the optoelectronic and photovoltaic device's application.
We report room temperature synthesis technique for the formamidinium lead iodide (FAPbI 3 ) perovskite. The low-cost sequential room temperature chemical synthesis technique resulted in formation of α-phase FAPbI 3 , suitable for solar cell absorber application. The chemical precursors formamidine acetate (CH 4 N 2 •xC 2 H 4 O 2 ) and lead iodide (PbI 2 ) were used in the process. The drop casted and spin coated films of FAPbI 3 on soda-lime glass and were then annealed at temperature of 80 °C. The FAPbI 3 materials films were characterized by X-ray diffraction, UV-Visible spectroscopy, photoluminescence (PL) measurements, and transmission electron microscopic (TEM) measurement. The X-ray diffraction pattern confirms α-phase of FAPbI 3 perovskite. The crystallite size as calculated from x-ray diffraction was found to be 40 nm corresponding to (001) peak. UV-Visible analysis shown broad absorption with bandgap value of 1.55 eV. The PL analysis show emission peak at 727 nm with estimated bandgap to be a 1.57 eV, in agreement with the UV-Visible spectroscopy. TEM analysis confirms the crystalline phase of FAPbI 3 material and the inter-planar spacing was deduced to be 0.62 nm. We conclude successful synthesis of FAPbI 3 perovskite with desirable properties in α-phase composition of FAPbI 3 that are suitable for solar cell application.
We report a facile synthesis of CuS and CdS nanoparticles using a cheap solution-processed chemical bath method forming heterogeneous nucleation. The optical, structural, photoelectrochemical (PEC), and electronic properties are studied by implementing relevant experimental techniques. The estimated optical band gap of ∼2.10 eV of CuS designates potential application in inexpensive photocatalysis and solar cells. Further, the valence band and conduction band positions of CuS and CdS are evaluated using cyclic voltammetry curves. Narrow conduction and valence band offset potentials measured at the CuS/CdS heterojunction are encouraging factors for the PEC application. The electronic properties are supported by the current density vs potential plots ( J – V ) with an improved short-circuit current density of 0.71 mA cm –2 for the heterojunction compared to bare CuS showing 0.15 μA cm –2 . The determined PCE of the heterojunction CuS/CdS is 0.65%.
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