Perovskite solar cells(PSCs)have attracted tremendous attention as a promising alternative candidate for clean energy genera-tion.Many attempts have been made with various deposition techniques to scale-up manufacturing.Slot-die coating is a robust and facile deposition technique that can be applied in large-area roll-to-roll(R2R)fabrication of thin film solar cells with the advantages of high material utilization,low cost and high throughput.Herein,we demonstrate the encouraging result of PSCs prepared by slot-die coating under ambient environment using a two-step sequential process whereby PbI2∶CsI is slot-die coated first followed by a subsequent slot-die coating of organic cations containing solution.A porous PbI2∶CsI film can promote the rapid and complete transformation into perovskite film.The crystallinity and morphology of perovskite films are significantly improved by optimizing nitrogen blowing and controlling substrate temperature.A power conversion efficiency(PCE)of 18.13％is achieved,which is promising for PSCs fabricated by two-step fully slot-die-coated devices.Furthermore,PSCs with a 1 cm2 area yield a champion PCE of 15.10％.Moreover,a PCE of 13.00％is obtained on a flexible substrate by the roll-to-roll(R2R)coating,which is one of the highest reported cells with all layers except for metal electrode fabricated by R2R process under ambient condition.