Recent Progress on Emerging Transparent Metallic Electrodes for Flexible Organic and Perovskite Photovoltaics

The rapid development of smart and wearable electronics calls for revolutionizing optoelectronics to become flexible, lightweight, and affordable. To meet these demands in photovoltaic devices, that is, solar cells, it is essential to develop mechanically flexible transparent electrodes over the conventional rigid ones while features such as low‐temperature procedures, stability, solution process, and/or low cost are highly desired and often required. Moreover, the optoelectronic properties of an electrode must not be compromised in an operational flexible cell. Despite the considerable challenges, various bendable transparent electrodes for solar cells have emerged in recent years. Particularly, transparent electrodes based on metallic materials are especially attractive as metal offers excellent conductivity and their formation processing is generally mature and commercially viable. This work aims to provide an overview of the recent development of metal‐based transparent electrodes for flexible organic and perovskite photovoltaics. After the introduction, metallic materials for the transparent electrodes including nanowires, meshes/grids, and films are discussed. The procedures and protocols for cell flexibility testing are summarized, before highlighting recent progress on fully functional, high‐efficiency flexible organic and perovskite solar cells using these transparent metallic electrodes. Finally, the challenges and outlook of the research field are discussed.