Fabrication of stable MAPbI3 perovskite via e-spray technique- hydration and phase reversibility

• Moisture affects perovskite thin film , promoting recrystallization or degradation based on hydration. • Reversible hydrated perovskite formation using electric-field-assisted spray coating is demonstrated. • Electric field alters perovskite phases; the resulting film has reduced hydration, enhancing stability. • Reversible hydration improves optoelectronic properties. • E-spray technique fabricates robust MAPI films with controlled hydration and reversibility. This study reports the fabrication of robust methylammonium lead iodide (MAPI) films via the e-spray technique, utilizing controlled and reversible hydration to enhance optoelectronic properties. Moisture in MAPI-based perovskite solar cells (PSCs) can either recrystallize or degrade the material, depending on the degree of hydration. The formation of hydrated perovskite phases (CH 3 NH 3 PbI 3 ·H 2 O and CH 3 NH 3 PbI 3 ·2H 2 O) and their phase reversibility are demonstrated in spray-coated MAPI films deposited under electric fields (E-fields). X-ray diffraction and absorption spectra reveal phase transitions influenced by the E-field during deposition. The resultant films, terminated with PbI 2 , exhibit reduced hydration (mono- or di-hydrated phases), forming a robust structure. Upon annealing, these hydrated phases revert to the perovskite phase. This work highlights the beneficial role of controlled hydration in MAPI films, offering insights into improving their stability and optoelectronic performance for PSC applications.