Exploring the impact of the Pb²⁺ substitution by Cd²⁺ on the structural and morphological properties of CH₃NH₃PbI₃ perovskite

Replacing the metal atoms in an organic–inorganic hybrid perovskite is of great significance to explore the low-toxic lead-free solar cells and other opto-electronic devices. In this work, we report the substitution of lead by 10% cadmium in CH₃NH₃PbI₃ hybrid perovskite samples synthesized in powder and thin-film forms. We have characterized their structural, morphological, optical and thermal properties using XRD, HR-TEM, SEM, DR UV–Vis spectroscopy and STA. The detailed structural analysis made through XRD, TEM and Rietveld refinement insights the structural phase transformation from tetragonal to cubic structure due to the incorporation of cadmium at lead sites. Controlled size and crystallinity are two crucial factors for solution which processed hybrid perovskite solar cells for device formation. Morphological studies reveal the improved crystallinity and an enhancement in grains sizes (> 8–9 times of pristine perovskite) with cadmium doping in pure perovskite structure. The DR UV–Vis spectroscopy shows the substantial reduction in the optical band gap and shifting of absorbance spectra towards NIR regions. These results open up the door for new perspicacity of transition metals to culminate lead-free designing of novel protective materials with advanced photovoltaic and photoelectric properties.