Heat‐Sink‐Free Flexible Organic Thermoelectric Generator Vertically Operating with Chevron Structure

Abstract Organic thermoelectric (TE) material receives increasing attention as a promising candidate for flexible TE generators, which is required for wearable applications such as self‐powered electronics, sustainable mobile batteries, and medical sensors. Recent advances in TE figure‐of‐merit of organic TE material reach that of bulk inorganic TE material. However, organic TE material is not fully functionalized to the TE generator, which shows low power output, operates in a lateral heat flow, and requires an additional heat sink. A flexible organic TE generator is presented herein by introducing an optimized solution process, chevron device structure, and a foam medium. Optimized poly(3,4‐ethylenedixoythiophene):polystyrene sulfonate (PEDOT:PSS) film involves a distinctive film morphology, achieving a high power factor (642 µW m −1 K −2 ) and a low sheet resistance (<10 Ω sq −1 ). A chevron‐structured TE generator, integrating 24 PEDOT:PSS patterns, is highly flexible and yields a remarkable TE output (≈1 µW at Δ T = 17.5 K) in a vertical heat flow. In addition, internal thermal transport through the device is systematically controlled by the inserted medium, which enables the heat‐sink‐free operation of the TE generator retaining 70% of its maximum voltage output in the absence of an additional heat sink.