Inkjet-Printed TiO2/Fullerene Composite Films for Planar Perovskite Solar Cells

Perovskite solar cells have garnered and held international research interest, due to ever-climbing power conversion efficiency values, now >25 %. Some high efficiency configurations utilize a compact TiO2 layer underneath a mesoporous TiO2 layer, both of which require high temperature annealing steps that could hinder perovskite commercialization. To address the high thermal budget, we chose to use inkjet-printing to combine the two layers into a single TiO2 film, which incorporates both nanoparticle and molecular precursor as well as organic fullerene additives. We printed the ink on fluorine-doped tin oxide, and after annealing at various temperatures, we found that 400 degrees C was the optimum annealing temperature for the inkjet-printed electron transport layers, which is significantly lower than the 500 degrees C required to anneal typical mesoporous TiO2 films.