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 (CH 3 NH 3 PbI 3 ) solar cell (PSC) with device architecture FTO/TiO 2 /Al 2 O 3 /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 (Al 2 O 3 ) or treatments such as heat and UV–O 3 treatments can affect the interfacial properties of this multilayer mesoporous structure. X-ray photoelectron spectra (XPS) show that UV–O 3 treatment increases the Ni 3+ (Ni 2 O 3 ) 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 CH 3 NH 3 PbI 3 formation inside the mesoporous layers by the PbI 2 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 Al 2 O 3 layer at 450 nm.