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

Abstract

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:NiOx 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:NiOx, is investigated. Thermal analysis studies using TGA and DTA reveal that the Cu:NiOx thin films show a more gradual mass loss while the bulk Cu:NiOx exhibits a distinct combustion process. The thin films can crystallize to Cu:NiOx 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:NiOx, including XPS, UV-Vis, AFM, and Contact angle measurements, is presented. Finally, 50 nm Cu:NiOx thin films are introduced as HTLs within the inverted perovskite solar cell device architecture. The Cu:NiOx HTL annealed at 150 and 200 °C provided PVSCs with limited functionality, whereas efficient triple-cation Cs0.04(MA0.17FA0.83)0.96 Pb(I0.83Br0.17)3-based PVSCs achieved for Cu:NiOx HTLs for annealing temperature of 300 °C.