Interfacial Investigation on Printable Carbon-Based Mesoscopic Perovskite Solar Cells with NiO_x/C Back Electrode

Solar cells with high efficiency, low cost, and high stability are the target for the new generation of solar cells. A fully printable perovskite (CH₃NH₃PbI₃) solar cell (PSC) with device architecture FTO/TiO₂/Al₂O₃/NiO_x/C is fabricated in the current research as a low-cost and relatively stable structure and is investigated to determine how different fabrication factors such as the thickness of the insulating spacer layer (Al₂O₃) or treatments such as heat and UV-O₃ treatments can affect the interfacial properties of this multilayer mesoporous structure. X-ray photoelectron spectra (XPS) show that UV-O₃ treatment increases the Ni³⁺(Ni₂O₃) phase on the surface of the black nickel oxide layer leading to better charge extraction and increasing open-circuit voltage (V_OC) up to 0.945 V. We observe improved CH₃NH₃PbI₃ formation inside the mesoporous layers by the PbI₂ penetration at a higher temperature. Impedance spectral together with current-voltage measurements show the effect of thickness for the insulator layer in the internal and interfacial resistances and photovoltaic characteristics of the cell. The best performance of the carbon-based PSC attains power conversion efficiency of 12.1% with the thickness of the Al₂O₃ layer at 450 nm.