All-Nanoparticle SnO2/TiO2 Electron-Transporting Layers Processed at Low Temperature for Efficient Thin-Film Perovskite Solar Cells

Solution-processed metal halide perovskite materials have revealed outstanding optoelectronic features that make them uniquely suited for photovoltaic applications. Although a rapid progress has led to performances similar to inorganic thin film technologies, the fabrication method of some of the most widely used electron selective layers, based on either mesoporous architectures or high annealing temperatures, may limit yet a future large-scale production. In that regard, planar perovskite solar cell configurations that can be processed at low temperatures are more desirable. Herein, we demonstrate that a few tens of nanometers thick bilayer, made of two types of inorganic oxide nanoparticles, can perform as a robust and low-temperature-processed electron-selective contact for planar perovskite solar cells. Aside from boosting the average efficiency of planar opaque devices, the proposed method allowed us to preserve the main photovoltaic characteristics when thinner active layers, usually exhibiting a noncontinuous morphology, were integrated for semitransparent cells. By providing excellent electronic and coverage features against the bottom electrode, this novel configuration may hence offer an alternative route to approach future inexpensive printable methodologies for the fabrication of efficient low-temperature perovskite solar cells.