Formamidinium lead iodide (FAPbI 3 ) 1,2 based perovskite solar cell (PSC) have emerged as the most promising cheaper photovoltaic technology with certified solar to power conversion efficiencies for single-junction >25% and perovskite-silicon tandem solar cells reaching ∼30%. There are two commonly known phases of this material: black phase and hexagonal yellow phase. Among these, thermodynamically stable hexagonal-FAPbI 3 is a photo-inactive material and consists of face-sharing Pb-I octahedral chains surrounded by 1 FA + cations. Alternatively, the metastable black-FAPbI 3 is made of corner-sharing Pb-I octahedra and a champion photo-active material commonly used to make highly efficient and stable PSCs.