Lattice Matching Using Spinel Oxides for Long Term Stability of Methylammonium-Free Lead Halide Perovskites

Perovskite solar cells still suffer from long term instability that can be linked to strain in the crystal structure induced during thermal annealing, causing defect formation, and ion migration. This work uses lattice matching to stabilize the cubic perovskite crystal structure and prevent secondary phase formation using a new family of materials: spinel oxides.<br/>Spinel oxides are promising candidates for lattice matching and heteroepitaxial growth due to their wide range of tunable lattice parameters, ability to be grown in thin layers through techniques like physical layer deposition, and potential for good band alignment. This work shows the use of spinel oxides as a lattice matching layer to stabilize the cubic Cs-FA perovskite phase. This study increases key understanding of crystallization and degradation of lead halide perovskites and proposes a potential method for fabricating more efficient and stable perovskite solar cells. Grazing incidence XRD and grazing incidence wide angle X-ray scattering (GIWAXS) are used to structurally characterize the effects of the lattice templating layer on the crystal structure from the surface to the bulk. Cathodoluminescence SEM goes even further to spatially correlate the morphology of templated and non-templated films to their optical properties. This study shows the potential for spinel oxides to be used as a lattice matching layer to facilitate heteroepitaxial growth of lead halide perovskites and improve long term stability by stabilizing the crystal structure.