Enhancing Efficiency and Stability of Tin-Based Perovskite Solar Cells Through the Addition of Nickel (II) Porphyrin Complex for Defect Passivation and Mitigation of Ion Migration

The stability and efficiency of tin perovskite solar cells (TPSCs) are often decreasing with high-density defects occurring at the grain boundaries of the perovskite film and the heterojunction interfaces of hole-transport material (HTM) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Hence, this study addresses these challenges using nickel (II) meso amino octaethylporphyrin (NiNH₂ OEP) as an effective defect-passivating agent for the device fabricated through a two-step method with an inverted device architecture. The precursor solution contains NiNH₂ OEP porphyrin coating over PEDOT:PSS, where NiNH₂ OEP is self-assembled uniformly at the perovskite grain boundary and interface between perovskite and HTM. NiNH₂ OEP is protonated to form nickel (II) ammonium porphyrin ions (NiNH₃⁺ OEP) to retard nonradiative charge recombination and inhibit ion migration that occurred through the high-density defect states to improve device stability and performance. Consequently, the TPSC device fabricated with NiNH₂ OEP unveils a remarkable power conversion efficiency of 9.6%. Moreover, the stability of the device shows a prominent improvement that maintains an initial efficiency of 90% for more than 6,000 h inside the glove box.