Effective interface treatment by zirconium acetylacetonate for inverted methylammonium-rich perovskite solar cells

Surface passivation of halide perovskites using suitable agents is crucial to enhance the performance of corre-sponding solar cells as surface defects dominate nonradiative recombination in the devices. Meantime, it is important to reduce surface recombination as well as improve the contact nature at the interface between perovskite and transport layers by introducing such an agent in devices. Many works have achieved remarkable results by designing novel interfacial modifiers, but it is still a challenge to realize excellent interface treatments by less-complicated small molecules. Here, we demonstrate that zirconium acetylacetonate (ZrAcac) provides both effective methylammonium-rich perovskites surface passivation and excellent interfacial charge transport channel between the perovskite and fullerene-based electron transport layer in inverted cell structure. We theoretically find that the deep in-gap states from the PbI and IPb anti-site defects are effectively eliminated by the strong interaction between ZrAcac and the perovskite surface, which is further confirmed by experimental Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Meantime, the suitable con-duction band minimum and deep valance band maximum of the ZrAcac on perovskites surface made a better electron transporting channel and interfacial anti-transfer barrier. Consequently, the corresponding device without encapsulation shows a power conversion efficiency (PCE) of 22.1% and still retains 80% of its initial PCE after 400 h of exposure to a constant environment (similar to 10% RH and 30 degrees C). This work provides a simple and cheap alternative perovskite interface treatment for future large-scale commercialization of perovskite solar cells.