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 (NiOx) hole transport layer are preferred for BIPVs due to their excellent stability and transparency. However, their performance is limited due to poor NiOx/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 NiOx/perovskite interface and study the effect of fluorine substitution on benzoic acid. Chemical interaction between these molecules and NiOx can remove hydroxyl groups from NiOx 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 approximate to 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.