Conformal zinc sulfide coating of vertically aligned ZnO nanorods by two-step hydrothermal synthesis on wide bandgap seed layers for lead-free perovskite solar cells.

Vertically aligned ZnO nanorods (NRs) were grown hydrothermally on the wide bandgap (∼3.86 - 4.04 eV) seed layers (SLs) of grain size ∼162 ± 35 nm, prepared using ball-milled derived ZnO powder. The synthesized ZnO NRs were further decorated with ZnS nanocrystals to achieve a ZnO NR-ZnS core-shell (CS)-like nano-scaffolds by a subsequent hydrothermal synthesis at 70 °C for 1 h. UV-Vis-NIR spectroscopy, x-ray diffractometry (XRD), Raman spectroscopy and Field emission scanning electron microscopy (FESEM) coupled with Energy dispersive x-ray spectroscopy (EDX) analyses confirmed the formation of ZnS atop the vertically aligned ZnO NR arrays of ∼1.79 ± 0.17µm length and ∼165 ± 27 nm diameter. Transmission electron microscopy (TEM)/EDX analyses revealed that vertically aligned ZnO NRs (core dia. ∼181 ± 12 nm) arrays are conformally coated by an ultrathin ZnS (∼25 ± 7 nm) shell layer with a preferential ZnS{111}/ZnO{10-10}-like partial epitaxy. The ZnO NRs exhibited a sharp band edge near ∼384 nm having optical bandgap energy (Eg) of ∼3.23 eV. However, the ZnO NR-ZnS CS exhibited double absorption bands atEg∼ 3.20 eV (ZnO-core) andEg∼ 3.78 eV (ZnS-shell). The ZnS{111}/ZnO{10-10}-nano-scaffolds could be utilized to facilitate the enhanced absorption of UV photons as well as the radial junction formation between the Pb-free perovskite absorber and ZnS/ZnO NRs layers.

Influence of Sn doping on the optoelectronic properties of ZnO nanoparticles.

Zinc Oxide (ZnO) nanoparticles (NPs) obtained a lot of attention from researchers and industries because of their superior properties as an optoelectronic material. Doping, especially tin (Sn), can further fine-tune their optoelectronic properties. In this manuscript, we have reported the optoelectronic properties of Sn-doped ZnO NPs, which were synthesized by a simple chemical solution method. A wide range of dopant (Sn) concentrations were used in the ratios of 0, 1, 3, 5, 7, and 10 weight percent. The effects of dopant (Sn) concentration on the structural, morphological, elemental composition, and optical properties of ZnO NPs were investigated by using an X-ray diffractometer (XRD), Field Emission Scanning Electron Microscope (FESEM), X-ray photoelectron spectrometer (XPS) and UV-Vis-NIR respectively. XRD analysis revealed the shifting of diffraction patterns towards a higher angle along with decreasing intensity. The calculated crystallite size using the XRD varied from 40.12 nm to 28.15 nm with an increasing doping percentage. Sn doping notably influences the size of ZnO NPs, along with crystal quality, strain, and dislocation density. The X-ray photoelectron spectroscopy (XPS) study showed the presence of zinc (Zn), oxygen (O), and tin (Sn) with their preferred oxidation states in the synthesized NPs. UV-Visible spectroscopy (UV-Vis) showed that the bandgap changed from 3.55 to 3.85 eV with the increasing concentration of Sn. FE-SEM revealed that the structures and surfaces were irregular and not homogeneous. The above findings for ZnO nanostructures show their potential application in optoelectronic devices.

Facile extraction and characterization of calcium hydroxide from paper mill waste sludge of Bangladesh.

Herein, paper mill waste sludge (PMS) from two different sources has been investigated to extract calcium hydroxide, Ca(OH)2 by a facile and inexpensive extraction process. PMS samples, collected from local paper mill plants of Bangladesh, were the main precursors wherein HCl and NaOH were used for chemical treatment. The as-synthesized products were analysed by a variety of characterization tools including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) elemental analyses. Our studies confirm that the extracted product contains Ca(OH)2 as a major content, albeit it also includes CaCO3 phase owing to the inescapable carbonation process from the surrounding environment. The particle size of the synthesized products is in the range of 450-500 nm estimated from SEM micrographs. The crystallite domain size of the same estimated from XRD analyses and was found to be approximately 47 and 31 nm respectively for product-A and product-B considering major (101) Bragg peak of Ca(OH)2. The yield percentage of the isolated products is about 65% for samples collected from both sources.

Facile synthesis of Cu2O nanorods in the presence of NaCl by successive ionic layer adsorption and reaction method and its characterizations.

Cuprous oxide (Cu2O) nanorods have been deposited on soda-lime glass substrates by the modified successive ionic layer adsorption and reaction technique by varying the concentration of NaCl electrolyte into the precursor complex solution. The structural, electrical and optical properties of synthesized Cu2O nanorod films have been studied by a variety of characterization tools. Structural analyses by X-ray diffraction confirmed the polycrystalline Cu2O phase with (111) preferential growth. Raman scattering spectroscopic measurements conducted at room temperature also showed characteristic peaks of the pure Cu2O phase. The surface resistivity of the Cu2O nanorod films decreased from 15 142 to 685 Ω.cm with the addition of NaCl from 0 to 4 mmol and then exhibited an opposite trend with further addition of NaCl. The optical bandgap of the synthesized Cu2O nanorod films was observed as 1.88-2.36 eV, while the temperature-dependent activation energies of the Cu2O films were measured as about 0.14-0.21 eV. Scanning electron microscope morphologies demonstrated Cu2O nanorods as well as closely packed spherical grains with the alteration of NaCl concentration. The Cu2O phase of nanorods was found stable up to 230°C corroborating the optical bandgap results of the same. The film fabricated in presence of 4 mmol of NaCl showed the lowest resistivity and activation energy as well as comparatively uniform nanorod morphology. Our studies demonstrate that the nominal presence of NaCl electrolytes in the precursor solutions has a significant impact on the physical properties of Cu2O nanorod films which could be beneficial in optoelectronic research.

Influence of the Substrate, Process Conditions, and Postannealing Temperature on the Properties of ZnO Thin Films Grown by the Successive Ionic Layer Adsorption and Reaction Method.

Here, we report the effect of the substrate, sonication process, and postannealing on the structural, morphological, and optical properties of ZnO thin films grown in the presence of isopropyl alcohol (IPA) at temperature 30-65 °C by the successive ionic layer adsorption and reaction (SILAR) method on both soda lime glass (SLG) and Cu foil. The X-ray diffraction (XRD) patterns confirmed the preferential growth thin films along (002) and (101) planes of the wurtzite ZnO structure when deposited on SLG and Cu foil substrates, respectively. Both XRD and Raman spectra confirmed the ZnO and Cu-oxide phases of the deposited films. The scanning electron microscopy image of the deposited films shows compact and uniformly distributed grains for samples grown without sonication while using IPA at temperatures 50 and 65 °C. The postannealing treatment improves the crystallinity of the films, further evident by XRD and transmission and reflection results. The estimated optical band gaps are in the range of 3.37-3.48 eV for the as-grown samples. Our experimental results revealed that high-quality ZnO thin films could be grown without sonication using an IPA dispersant at 50 °C, which is much lower than the reported results using the SILAR method. This study suggests that in the presence of IPA, the SLG substrate results in better c-axis-oriented ZnO thin films than that of deionized water, ethylene glycol, and propylene glycol at the optimum temperature of 50 °C. Air annealing of the samples grown on Cu foils induced the formation of Cu x O/ZnO junctions, which is evident from the characteristic I-V curve including the structural and optical data.

The effect of substrate temperature and oxygen partial pressure on the properties of nanocrystalline copper oxide thin films grown by pulsed laser deposition.

The data presented in this paper are related to the research article entitled "Pulsed laser deposition of single phase n- and p-type Cu2O thin films with low resistivity" (S.F.U. Farhad et al., 2020) [1]. The detailed processing conditions of copper oxide thin films and a variety of characterization techniques used are described in the same ref. [1]https://doi.org/10.1016/j.matdes.2020.108848. Thin films need to grow on different substrates to elucidate various properties of the individual layer for attaining optimum processing conditions required for devising efficient optoelectronic junctions as well as thin film stacks for different sensing applications. This article describes the effect of substrate temperature and oxygen partial pressure on the structural, morphological, optical, and electrical properties of pulsed laser deposited (PLD) nanocrystalline copper oxide thin films on quartz glass, ITO, NaCl(100), Si(100), ZnO coated FTO substrates. The low temperature grown copper oxide and zinc oxide thin films by PLD were used for devising solid n-ZnO/p-Cu2O junction and investigated their photovoltaic and interface properties using dynamic photo-transient current measurement at zero bias voltage and TEM/EDX respectively. These datasets are made publicly available for enabling extended analyses and as a guide for further research.