Iontronically Tunable Broadband Graded Index Films

Abstract Tunable optical devices are of paramount importance in modern optical engineering, offering the flexibility to dynamically adjust key optical parameters, thus enhancing functionality and adaptability. In this study, a fresh approach is presented to achieve on‐demand, spatially tunable optical properties using organic mixed ion‐electron conductors, which can be produced using large‐scale, cost‐effective technologies. It is demonstrated how, by exploiting, the spatial modulation of the bulk electronic conductance of PEDOT:PSS through an organic electrochemical transistor configuration, we can create a spatially tunable broadband gradient index profile with multiple degrees of freedom. These findings introduce a new class of tunable graded index media, which hold potential for a wide range of applications that span from optical interconnections to multi‐focal optical devices.