Polymer‐Assisted Heterogeneous Lead Iodide in a Two‐Step Process: Fabrication of Efficient and Stable Perovskite Solar Cells

Developing pinhole‐free, superior crystal, and high‐quality perovskite films by regulating the lead iodide microstructure in two‐step sequential deposition has attracted increased interest in the domain of perovskite solar cells (PSCs) for commercial applications. Herein, a multifunctional polymer, polyvinyl alcohol (PVA), is incorporated into a two‐step sequential deposition process to regulate morphological transform of PbI 2 and then the high‐quality perovskite films are obtained. PVA as a scaffold combines with uncoordinated Pb 2+ in the PbI 2 precursor solution through a strong Pb–O interaction, leading to rough PbI 2 . In the second step, the uneven and heterogeneous PbI 2 allows FA&MA permeation and then drives adequate coordination reactions between PbI 6 4− octahedron and bulky cations. Furthermore, the PVA gathering at grain boundary passivates redundant Pb 2+ by the PbO bonding interactions in the final polycrystalline films. Consequently, high‐quality (FAPbI 3 ) 0.90 (MAPbBr 3 ) 0.10 perovskite layers are obtained with promoted crystal growth, inhibited voids formation/delamination, and thus reduced trap states. The universality and versatility of this strategy not only enables improved power conversion efficiencies of 22.81% (Ag‐based devices) and 16.58% (carbon‐based devices) across architectures but also remarkedly enhances the device stability in ambient‐air aging condition, which delivers a facile and broadly applicable additive synergetic strategy for efficient and stable PSCs.