2D Perovskite Seeds Enabled High-Quality Perovskite Films with Facet Orientation and Released Stresses on Flexible Substrates

Organic–inorganic halide perovskite,the light absorber of flexible perovskite solar cells (f-PSCs), suffered from poor quality of perovskite films on a flexible substrate, which made the efficiency of f-PSCs lag behind that of rigid perovskite solar cells. Here, an organic cation of 4-pyridinylmethylammonium iodide (4-PyAI) was screened to form two-dimensional (2D) perovskite as "seeds" for gaining three-dimensional (3D) perovskite thin films. Because the introduction of 2D perovskites significantly optimized the process of perovskite film crystallization, superior perovskite film quality was observed along with highly orientated perovskite crystals. As a result, high efficiencies of 21.97% were obtained for the f-PSCs. On the other hand, the f-PSCs showed excellent mechanical performances due to 2D perovskite, remaining 90% of the initial power conversion efficiency (PCE) after 2500 times bending.