Facile Dimension Transformation Strategy for Fabrication of Efficient and Stable CsPbI3 Perovskite Solar Cells

All-inorganic cesium lead triiodide (CsPbI3) perovskite has received increasing attention due to its intrinsic thermal stability and suitable band gap for photovoltaic applications. However, it is difficult to deposit high-quality pure-phase CsPbI3 films using CsI and PbI2 as precursors due to the rapid nucleation and crystal growth by the solution coating method. Here, a simple cation-exchange approach is employed to fabricate all-inorganic 3D CsPbI3 perovskite, where 1D ethylammonium lead (EAPbI3) perovskite is first solution-deposited and then transformed to 3D CsPbI3 via ion exchange between EA+ and Cs+ during thermal annealing. The large space between the PbI3– skeletons in 1D EAPbI3 favors the cation interdiffusion and exchange for the formation of pure-phase 3D CsPbI3 with full compactness and high crystallinity and orientation. The resulting CsPbI3 film exhibits a low trap density of state and high charge mobility, and the perovskite solar cell shows a power-conversion efficiency of 18.2% with enhanced stability. This strategy provides an alternative and promising fabrication route for the fabrication of high-quality all-inorganic perovskite devices.