Foldable perovskite solar cells and modules enabled by mechanically engineered ultrathin indium-tin-oxide electrodes

Flexible transparent conducting electrodes (TCEs) play a critical role when achieving highly flexible perovskite solar cells (PSCs) for potential applications such as wearable, portable, and aerospace power sources. Despite extensive exploration of electrode materials and substrate engineering, there have been few reports on flexible PSCs with both satisfactory performance and flexibility. Here, highly conductive indium-tin-oxide (ITO) based ultrathin TCEs are developed for highly efficient, and foldable perovskite solar cells and modules. By introducing an additional aluminum oxide (AlO${}_x$) layer to the substrate, deformation-free ITO-based ultrathin (≈10 µm) TCEs are successfully fabricated. A champion flexible perovskite solar cell and module using ultrathin TCEs achieve efficiencies of 19.16% and 13.26% (aperture areas of 0.078 and 16 cm${}^2$), respectively, outperforming reference devices using commercial high-performing flexible TCEs. The modules maintain 100% and 92% of their initial performance after 10 000 bending cycles with a radius of 1 and 0.5 mm, respectively, which is unprecedented on module scale. (© 2022 Wiley‐VCH GmbH)