Despite the astonishing progress reached in the last five years, perovskite films still lack some stability. It is well known that UV light and humidity affect strongly perovskite-based solar cell ...performances. We herein investigate the degradation process of perovskite-based CH3NH3PbI3 thin films without encapsulation in presence of direct UV light. The UV irradiation effect on structural, morphological and optical properties of the perovskite thin film is studied. Experimental results show significant degradation of perovskite properties after 12 h of exposure to UV light. The main objective of this work is to show that it is possible to improve the MAPbI3 stability upon UV by the adequate incorporation of the bromide atoms in the perovskite matrix. In fact, it has been found that the CH3NH3Pb(I1-xBrx)3 perovskite exhibits a better stability, distinctly when the bromide fraction is above 20%. We believe that the observed improvement is linked to the structural transition from the tetragonal phase to the more stable cubic structure as shown by the XRD results.
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•CH3NH3Pb(I1-xBrx)3 perovskite films were prepared using spin coating technique.•The effect of UV irradiation on CH3NH3Pb(I1-xBrx)3 was studied.•CH3NH3Pb(I1-xBrx)3 films with more than 20% of Br exhibit a good UV stability.•Detailed structural and optical characterization are reported.
Herein the growth mechanism of an un-doped zinc oxide (i-ZnO) and an Al-doped zinc oxide (AZO) was investigated using electrochemical techniques. Zinc and aluminum nitrates precursors were used in an ...aqueous bath solution, under a fixed potential of about –1.0 V, at 80°C. The variations of the morphological, structural, and optical properties of AZO were investigated in terms of Al
3+
concentrations ranging from 0 to 4 atomic percentage in the starting solution. The X-ray diffraction patterns showed the hexagonal wurtzite structure for all samples. The effect of the lateral growth mechanism of AZO instead of the longitudinal growth process of ZnO was confirmed by calculating the texture coefficient and by studying the surface morphology under high magnification via scanning electron microscopy. It was found that the morphology evolved from hexagonal flat nanorods into a mixture of tapered hexagonal nanorods and nanosheets, to larger nanosheets by adding aluminum ions dopants. All films demonstrated a transmittance of about 80% in the visible range and exhibited a slight red shift in the absorption edge with Al
3+
doping. The optical band gap of AZO nanosheets was found to be lower than that of i-ZnO nanorods. These findings provide fundamental understanding of the growth mechanism and shape control of a nanostructured zinc oxide.
In this work, thin CdS films have been deposited using the chemical bath deposition technique (CBD). Different synthesis parameters, such as number of runs, deposition time, and postannealing ...temperature, are studied and optimized in order to avoid the supersaturation phenomenon and to achieve a low-temperature growth. CdS thin films, of cubic structure, oriented along the (111) direction with homogenous and smooth surface, have been deposited by using the CBD growth process without any annealing treatment. Based on a set of experimental observations, we show that the solution saturation phenomenon can be avoided if the deposition is performed in several runs at a short deposition time. Throughout the CBD technique, it is then possible not only to overcome any film thickness limitation but also to grow the CdS films in a single technological step at a low temperature and without any postdeposition annealing treatment. CdS films with excellent structural quality and a controllable thickness are obtained when the deposition bath temperature is fixed at 65°C. In addition, deposited films exhibit an optical transmittance ranging from 70 to 95% depending on the synthesis parameters, with band gap energy around 2.42 eV. The process developed in this work might be useful for depositing CdS films on flexible substrates.
•X-ray diffraction analyses indicate the formation of a tetragonal phase I4/mcm up to x=0.4 and a cubic perovskite with space group Pm3m across in the composition range of 0.6≤x≤1.•Perovskite films ...exhibit a very high absorbance in the visible and short infrared.•As the fraction of bromide change, the adsorption edge of thin film perovskite can be tuned along the visible spectrum from 543nm to 785nm.•The incorporating of bromide into MAPbI3−xBrx shifts the PL emission to shorter wavelengths.
Mixed bromide iodide lead perovskites were prepared from methylamine, lead nitrate and the corresponding hydroX acid (X=I, Br), they were then deposited as thin films on ITO substrate by the spin coating process. X-ray diffraction analyses indicated the formation of a tetragonal phase I4/mcm up to x=0.4 and a cubic perovskite with space group Pm3m in the composition range of 0.6≤x≤1. Mixed lead perovskites showed a high absorbance in the UV–vis range. The band gap energy of thin films were estimated from absorbance spectral measurements, it was found that the onset of the absorption edge for MAPbI3−xBrx (x<1) thin films is ranging between 1.58 to 1.72eV. Photoluminescence emission energies for mixed halide perovskites presented intermediate values from 781nm (MAPbI3) to 545nm (MAPbBr3).
The increasing CO 2 concentration in the atmosphere has caused profound environmental issues such as global warming. The use of CO 2 as a feedstock to replace traditional fossil sources holds great ...promise to reduce CO 2 emissions. The electrochemical conversion of CO 2 has attracted much attention because it can be powered by renewable sources such as solar energy. In this review article, we provide insight into the important parameters when studying CO 2 RR and give a comprehensive review on the description of synthesis methods with electrocatalytic CO 2 reduction over bimetallic copper-based materials. Due to the important bibliographic data on Cu bimetallic materials, we have limited this review to Sn, In, Pd, Zn and Ag. At the end of this review, challenges and perspectives for further upgrading have been included to briefly highlight the important future considerations of this rapidly growing technology.
This study sheds light on the effect of iodide substitution on the structural and optical properties of solution processed mixed cesium lead perovskite thin films CsPbBr3−xIx (0 ≤ x ≤ 1) as well as ...their atmospheric and thermal stability. Pawley fit indicated that the mixed lead halide CsPbBr3−xIx perovskite crystallizes in the orthorhombic (Pnma) space group. X-ray diffraction analyses showed a shift to lower angles when the average fraction of iodide incorporated increased indicating the expansion of the lattice. Absorbance measurements show that the CsPbBr3−xIx films exhibit a very high absorbance in the visible and short infrared region. The band gap of CsPbBr3−xIx is tuned from 2.38 (CsPbBr3) to 2.17 eV (CsPbBr2I1) following the Vegard's law. CsPbBr3 films showed a bright photoluminescence with emission maximum at 530 nm CsPbBr3−xIx films demonstrate excellent stability after aging for two days in a humid environment (relative humidity of ∼60%) and under thermal annealing at relatively high temperature.
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•Band gap of the CsPbBr3−xIx films can be tuned from 2.38 to 2.16 eV following the Vegard's law.•CsPbBr3−xIx films exhibit high absorbance.•CsPbBr3−xIx films are thermally and atmospherically stable.•CsPbBr3−xIx films crystallize in orthorhombic (Pnma) space group.•Iodine substitution leads to an expansion of the lattice and a shift of the absorbance onset.
Antisolvent behavior is one of the most important treatments for producing high-quality perovskite MaPbI
3
thin films. However, the optimization of the amount of antisolvent used has not been ...analyzed on a uniform platform. In this work, a systematic study is employed to quantitively evaluate the impact of anti-solvent treatment on the morphological, structural, and optoelectronic characteristics of MAPbI
3
films. The results confirm that an adequate amount of 2.5 ml with a slow annealing treatment leads to homogeneous perovskite films with virtually no holes and large grain size. Using antisolvent treatment and optimized thermal annealing, we were able to control the nucleation and growth of the MAPbI
3
, and therefore achieve highly compact perovskite films with large grains, excellent crystalline quality, and very low pinhole density. The results of this study could help establish reproducible manufacturing processes for perovskite solar cells.
The increasing CO2 concentration in the atmosphere has caused profound environmental issues such as global warming. The use of CO2 as a feedstock to replace traditional fossil sources holds great ...promise to reduce CO2 emissions. The electrochemical conversion of CO2 has attracted much attention because it can be powered by renewable sources such as solar energy. In this review article, we provide insight into the important parameters when studying CO2RR and give a comprehensive review on the description of synthesis methods with electrocatalytic CO2 reduction over bimetallic copper-based materials. Due to the important bibliographic data on Cu bimetallic materials, we have limited this review to Sn, In, Pd, Zn and Ag. At the end of this review, challenges and perspectives for further upgrading have been included to briefly highlight the important future considerations of this rapidly growing technology.
In this study, we demonstrate that the crystallization process of CsPbI2Br films can be modulated when small amounts of additives are added to the precursor solution, leading to the formation of the ...bright brownish α-phase perovskite films with high orientation along the 100 crystallographic direction. Doped CsPbI2Br films exhibit improved crystallinity, with high coverage, large grain size and pinhole-free surface morphology, suitable for making high performance optoelectronic devices. We also explored the role of Cl in the photophysical properties of CsPbI2Br perovskite films using the temperature dependent photoluminescence technique. We found that the Cl ions enhance the photoluminescence emission by reducing the density of trap states, and also decrease the exciton binding energy from (22 ± 3) meV to (11 ± 2) meV. We believe this work contributes to understanding the effect of doping on the crystallization process with an in-depth insight into the photophysical properties of the cesium-based perovskite materials.
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