Efficient Flexible Monolithic Perovskite/CIGS Tandem Solar Cell by Using Two‐Step Hybrid Deposition Approach

ABSTRACT Flexible perovskite/CIGS tandem solar cells offer a promising route toward lightweight, high‐efficiency photovoltaics for emerging applications, yet challenges related to perovskite instability remain critical obstacles. Here, we report a first highly efficient monolithic flexible perovskite/CIGS solar cell fabricated via a two‐step hybrid (co‐evaporation‐solution) process. This method enables conformal and pinhole‐free perovskite films on CIGS by suppressing Zn‐induced degradation through a novel low‐temperature process. Although the reduced process temperature led to suboptimal perovskite microstructure, the introduction of Lewis base additive engineering significantly improved film crystallinity and device performance. The resulting device achieves a PCE of 26.01% (certified PCE of 25.9%) with a record V OC of 1.85 V without employing a NiO x hole transport layer. Extending the same process to a flexible polyimide substrate yields 26.4%. This scalable, NiO x ‐free hybrid strategy establishes a pathway for high‐efficiency, flexible and lightweight photovoltaics.