High-Performance n-Type Organic Thermoelectrics with Exceptional Conductivity by Polymer-Dopant Matching

초록

Achieving high electrical conductivity (sigma) and power factor (PF) simultaneously remains a significant challenge for n-type organic themoelectrics (OTEs). Herein, we demonstrate the state-of-the-art OTEs performance through blending a fused bithiophene imide dimer-based polymer f-BTI2g-SVSCN and its selenophene-substituted analogue f-BSeI2g-SVSCN with a julolidine-functionalized benzimidazoline n-dopant JLBI, vis-& agrave;-vis when blended with commercially available n-dopants TAM and N-DMBI. The advantages of introducing a more lipophilic julolidine group into the dopant structure of JLBI are evidenced by the enhanced OTEs performance that JLBI-doped films show when compared to those doped with N-DMBI or TAM. In fact, thanks to the enhanced intermolecular interactions and the lower-lying LUMO level enabled by the increase of selenophene content in polymer backbone, JLBI-doped films of f-BSeI2g-SVSCN exhibit a unprecedent sigma of 206 S cm-1 and a PF of 114 mu W m-1 K-2. Interestingly, sigma can be further enhanced up to 326 S cm-1 by using TAM dopant as a consequence of its favorable diffusion behavior into densely packed crystalline domains. These values are the highest to date for solution-processed molecularly n-doped polymers, demonstrating the effectiveness of the polymer-dopant matching approach carried out in this work. Impressive n-type thermoelectric performances with a conductivity of 326 S cm-1 and power factor as high as 114 mu Wm-1 K-2 were realized through the approach of polymer-dopant matching, which involved blending two n-type polymers, f-BTI2g-SVSCN and f-BSeI2g-SVSCN, with a julolidine functionalized benzimidazoline n-dopant (JLBI) in addition to the state-of-the-art TAM and N-DMBI dopants. image

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