Electrocatalytic water splitting is a promising solution to resolve the global energy crisis. Tuning the morphology and particle size is a crucial aspect in designing a highly efficient nanomaterials-based electrocatalyst for water splitting. Herein, green synthesis of nickel oxide nanoparticles using phytochemicals from three different sources was employed to synthesize nickel oxide nanoparticles (NiO_x NPs). Nickel (II) acetate tetrahydrate was reacted in presence of aloe vera leaves extract, papaya peel extract and dragon fruit peel extract, respectively, and the physicochemical properties of the biosynthesized NPs were compared to sodium hydroxide (NaOH)-mediated NiO_x. Based on the average particle size calculation from Scherrer’s equation, using X-ray diffractograms and field-emission scanning electron microscope analysis revealed that all three biosynthesized NiO_x NPs have smaller particle size than that synthesized using the base. Aloe-vera-mediated NiO_x NPs exhibited the best electrocatalytic performance with an overpotential of 413 mV at 10 mA cm⁻² and a Tafel slope of 95 mV dec⁻¹. Electrochemical surface area (ECSA) measurement and electrochemical impedance spectroscopic analysis verified that the high surface area, efficient charge-transfer kinetics and higher conductivity of aloe-vera-mediated NiO_x NPs contribute to its low overpotential values.

An ideal n-i-p perovskite solar cell employing a Pb free CH₃NH₃SnI₃ absorber layer was suggested and modelled. A comparative study for different electron transport materials has been performed for three devices keeping CuO hole transport material (HTL) constant. SCAPS-1D numerical simulator is used to quantify the effects of amphoteric defect based on CH₃NH₃SnI₃ absorber layer and the interface characteristics of both the electron transport layer (ETL) and hole transport layer (HTL). The study demonstrates that amphoteric defects in the absorber layer impact device performance significantly more than interface defects (IDL). The cell performed best at room temperature. Due to a reduction in V_oc, PCE decreases with temperature. Defect tolerance limit for IL1 is 10¹³ cm⁻³, 10¹⁶ cm⁻³ and 10¹² cm⁻³ for structures 1, 2 and 3 respectively. The defect tolerance limit for IL2 is 10¹⁴ cm⁻³. With the proposed device structure FTO/PCBM/CH₃NH₃SnI₃/CuO shows the maximum efficiency of 25.45% (V_oc = 0.97 V, J_sc = 35.19 mA/cm², FF = 74.38%), for the structure FTO/TiO₂/CH₃NH₃SnI₃/CuO the best PCE is obtained 26.92% (V_oc = 0.99 V, J_sc = 36.81 mA/cm², FF = 73.80%) and device structure of FTO/WO₃/CH₃NH₃SnI₃/CuO gives the maximum efficiency 24.57% (V_oc = 0.90 V, J_sc = 36.73 mA/cm², FF = 74.93%) under optimum conditions. Compared to others, the FTO/TiO₂/CH₃NH₃SnI₃/CuO system provides better performance and better defect tolerance capacity.

In this study, lead sulfide (PbS) nanoparticles were synthesized by the chemical precipitation method using Aloe Vera extract with PbCl₂ and Thiourea (H₂N-CS-NH₂). The synthesized nanoparticles have been investigated using x-ray diffraction (XRD), UV-Vis, energy-dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD and TEM results confirm that the films are in the cubic phase. The crystallite size, lattice constant, micro-strain, dislocation density, optical bandgap, etc. have been determined using XRD and UV-Vis for investigating the quality of prepared nanoparticles. The possible application of these synthesized nanoparticles in the solar cells was investigated by fabricating the thin films on an FTO-coated and bare glass substrate. The properties of nanoparticles were found to be nearly retained in the film state as well. The experimentally found properties of thin films have been implemented for perovskite solar cell simulation and current-voltage and capacitance-voltage characteristics have been investigated. The simulation results showed that PbS nanoparticles could be a potential hole transport layer for high-efficiency perovskite solar cell applications.