Scalable Fabrication of >90 cm2 Perovskite Solar Modules with >1000 h Operational Stability Based on the Intermediate Phase Strategy

In addition to high efficiencies, upscaling and long-term operational stability are key pre-requisites for moving perovskite solar cells toward commercial applications. In this work, a strategy to fabricate large-area uniform and dense perovskite films with a thickness over one-micrometer via a two-step coating process by introducing NH4Cl as an additive in the PbI2 precursor solution is developed. Incorporation of NH4Cl induces the formation of the intermediate phases of x[NH4+]center dot[PbI2Clx](x)(-) and HPbI3-xClx, which can effectively retard the crystallization rate of perovskite leading to uniform and compact full-coverage perovskite layers across large areas with high crystallinity, large grain sizes, and small surface roughness. The 5 x 5 and 10 x 10 cm(2) perovskite solar modules (PSMs) based on this method achieve a power conversion efficiency (PCE) of 14.55% and 10.25%, respectively. These PSMs also exhibit good operational stability with a T-80 lifetime (the time during which the solar module PCE drops to 80% of its initial value) under continuous light illumination exceeding 1600 h (5 x 5 cm(2)) and 1100 h (10 x 10 cm(2)), respectively.