Sequential Dip-spin Coating Method: Fully Infiltration of MAPbI3-xClx into Mesoporous TiO2 for Stable Hybrid Perovskite Solar Cells

- Sequential dip-spin coating method is developed to coat a uniform perovskite film without voids.
- The dip-spin coated perovskite film increases the recombination resistance owing to complete pore-filling, enhancing the JSC and PCE.
- A void-free and pore-filled perovskite film with large grains (average 2.10 μm) is achieved by the dip-spin coating.
- The pore-filled and void-free perovskite film fabricated via dip-spin coating prevents the diffusion.
- The cell fabricated via the dip-spin coating maintains 99% of their initial PCE after 35 days of storage.

Organic-inorganic hybrid perovskite solar cells (PSCs) have reached a power conversion efficiency of 22.1% in a short period (∼7 years), which has been obtainable in silicon-based solar cells for decades. The high power conversion efficiency and simple fabrication process render perovskite solar cells as potential future power generators, after overcoming the lack of long-term stability, for which the deposition of void-free and pore-filled perovskite films on mesoporous TiO2 layers is the key pursuit. In this research, we developed a sequential dip-spin coating method in which the perovskite solution can easily infiltrate the pores within the TiO2 nanoparticulate layer, and the resultant film has large crystalline grains without voids between them. As a result, a higher short circuit current is achieved owing to the large interfacial area of TiO2/perovskite, along with enhanced power conversion efficiency, compared to the conventional spin coating method. The as-made pore-filled and void-free perovskite film avoids intrinsic moisture and air and can effectively protect the diffusion of degradation factors into the perovskite film, which is advantageous for the long-term stability of PSCs.