ABSTRACT
CdS, characterized by its comparatively narrow energy band gap (â¼2.4 eV), is an appropriate material for prospective use as a photoanode in photoelectrochemical water splitting. Regrettably, it encounters several obstacles for practical and large-scale applications, including issues such as bulk carrier recombination and diminished conductivity. Here, we have tried to address these challenges by fabricating a novel photoelectrode (ZnO/CdS) composed of one-dimensional ZnO nanorods (NRs) decorated with two-dimensional CdS nanosheets (NSs). A facile two-step chemical method comprising electrodeposition along with chemical bath deposition is employed to synthesize the ZnO NRs, CdS NSs, and ZnO/CdS nanostructures. The prepared nanostructures have been investigated by UV-visible absorption spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy. The fabricated ZnO/CdS nanostructures have shown enhanced photoelectrochemical properties due to the improvement of the semiconductor junction surface area and thereby enhanced visible light absorption. The incorporation of CdS NSs has been further found to promote the rate of the charge separation and transfer process. Subsequently, the fabricated ZnO/CdS photoelectrodes achieved a photocurrent conversion efficiency 3 times higher than that of a planar ZnO NR photoanode and showed excellent performance under visible light irradiation. The highest applied bias photon-to-current conversion efficiency (% ABPE) of about â¼0.63% has been obtained for the sample with thicker CdS NSs on ZnO NRs with a photocurrent density of â¼1.87 mA/cm2 under AM 1.5 G illumination. The newly synthesized nanostructures further demonstrate that the full photovoltaic capacity of nanomaterials is yet to be exhausted.
ABSTRACT
A comprehensive study regarding the effect of different solvent vapours on organolead halide perovskite properties is lacking. In the present work, the impact of exposing CH3NH3PbI3 films to the vapours of commonly available solvents has been studied. The interaction with perovskite has been correlated to solvent properties like dielectric constant, molecular dipole moment, Gutmann donor number and boiling point. Changes in the crystallinity, phase, optical absorption, morphologies at both nanometer and micrometer scale, functional groups and structures were studied using X-ray diffraction, UV-visible absorption, FE-SEM, FTIR and Raman spectroscopies. Among the aprotic solvents DMSO and DMF vapours deteriorate the crystallinity, phase, and optical, morphological and structural properties of the perovskite films in a very short time, but due to the difference in solvent property values acetone affects the perovskite properties differently. Polar protic 2-propanol and water vapours moderately affect the perovskite properties. However 2-propanol can solvate the organic cation CH3NH3 + more efficiently as compared to water and a considerable difference was found in the film properties especially the morphology at the nanoscale. Nonpolar chlorobenzene vapour minutely affects the perovskite morphology but toluene was found to enhance perovskite crystallinity. Solvent properties can be effectively used to interpret the coordination ability of a solvent. The present study can be immensely useful in understanding the effects of different solvent vapours and also their use for post-deposition processing (like solvent vapour annealing) to improve their properties.
