Thermoelectric Performance of n-Type Conjugated Polymer Based on a Quinoidal Unit of Benzodipyrrolidone

Effective charge transport properties and molecular doping efficiency are pivotal for achieving a high performance in organic thermoelectrics (OTEs). However, a significant challenge has been the scarcity of electron-deficient building blocks suitable for polymer construction. To address this shortfall, we introduce the quinoidal unit benzodipyrrolidone (BDP) into the realm of organic thermoelectrics for the first time. This work investigates the n-doping and thermoelectric properties of two BDP-based n-type polymers, PBDP-2F and PBDP-2CN. Notably, PBDP-2CN exhibited an E LUMO of -4.13 eV, representing a 0.11 eV reduction compared to PBDP-2F. Due to its high electron affinity, PBDP-2CN can be doped more easily than PBDP-2F, resulting in higher thermoelectric performance. Furthermore, our comparative analysis with Raman spectroscopy highlighted the exceptional structural stability of quinoidal-based polymers, as evidenced by the preservation of vibrational modes upon doping compared to P(NDI2OD-T2). This significant contribution heralds the innovative use of BDP as a building block in OTEs and yields crucial insights into the molecular design of n-type polymers for achieving a superior thermoelectric performance.