Thermal Analysis of Metal-Organic Precursors for Functional Cu:ΝiOx Hole Transporting Layer in Inverted Perovskite Solar Cells: Role of Solution Combustion Chemistry in Cu:ΝiOx Thin Films Processing.

Low temperature solution combustion synthesis emerges as a facile method for the synthesis of functional metal oxides thin films for electronic applications. We study the solution combustion synthesis process of Cu:NiO using different molar ratios (w/o, 0.1 and 1.5) of fuel acetylacetone (Acac) to oxidizer (Cu, Ni Nitrates) as a function of thermal annealing temperatures 150, 200, and 300 °C. The solution combustion synthesis process, in both thin films and bulk Cu:NiO, is investigated. Thermal analysis studies using TGA and DTA reveal that the Cu:NiO thin films show a more gradual mass loss while the bulk Cu:NiO exhibits a distinct combustion process. The thin films can crystallize to Cu:NiO at an annealing temperature of 300 °C, irrespective of the Acac/Oxidizer ratio, whereas lower annealing temperatures (150 and 200 °C) produce amorphous materials. A detail characterization study of solution combustion synthesized Cu:NiO, including XPS, UV-Vis, AFM, and Contact angle measurements, is presented. Finally, 50 nm Cu:NiO thin films are introduced as HTLs within the inverted perovskite solar cell device architecture. The Cu:NiO HTL annealed at 150 and 200 °C provided PVSCs with limited functionality, whereas efficient triple-cation Cs(MAFA) Pb(IBr)-based PVSCs achieved for Cu:NiO HTLs for annealing temperature of 300 °C.