Enhanced perovskite solar cells performance with TiO_x and SnO_x thin films as electron transport layers

We report on the potential application of crystalline thin metal oxide films (TiOx, SnOx) with varying stoichiometries in perovskite solar cell devices. The oxides were deposited via reactive e-beam evaporation, involving the sublimation of pure metals under different pressures of pure oxygen, followed by thermal annealing at 200 degrees C. Variable angle spectroscopic ellipsometry, X-ray diffraction (XRD), contact angle measurements, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the films. XRD findings confirmed the crystalline phases of SnOx thin films treated at 200 degrees C for the most oxygen-rich films (deposited at 2e-4 Torr), while TiOx layers exhibited an amorphous phase. FESEM results confirmed that uniform and dense films were generated across the entire substrate surface. Using the measured refractive indices in a computational model, it was demonstrated that optimizing the device design with these films could result in power conversion efficiencies surpassing 25%.