Buried Interfacial Passivation in NiOx-Based Inverted Semi-Transparent Perovskite Solar Cells

Semi-transparent perovskite solar cells (STPSCs) have shown great potential in Building Integrated Photovoltaics (BIPVs). Inverted STPSCs with nickel oxide (NiO_x) hole transport layer are preferred for BIPVs due to their excellent stability and transparency. However, their performance is limited due to poor NiO_x/perovskite interface leading to non-radiative recombination and perovskite degradation. Here, the study uses different fluorinated benzoic acids viz. 4-fluorobenzoic acid, 3,4-di-fluorobenzoic acid, and 3,4,5-tri-fluorobenzoic acid, to improve NiO_x/perovskite interface and study the effect of fluorine substitution on benzoic acid. Chemical interaction between these molecules and NiO_x can remove hydroxyl groups from NiO_x surface, mitigating defect states which results in reduced non-radiative recombination. STPSCs modified with 4-fluorobenzoic acid demonstrate a champion power conversion efficiency (PCE) of 15.12% with an average visible transmittance (AVT) of ≈30%. Modified unencapsulated device maintains 90% of its initial PCE after 1500 hours, stored in 30-35% humidity, demonstrating its superior stability. This study emphasizes the role of buried interfacial passivation in development of STPSCs for building facades, windows, or skylights.