Sequential p-type doping of polytriphenylamine–SWCNT composites by tris(pentafluorophenyl)borane for high-performance flexible thermoelectrics

Abstract

Organic thermoelectric materials offer sustainable alternatives to conventional inorganic systems but are limited by low electrical conductivity and weak thermal stability. Here, we demonstrate the first thermoelectric application of polytriphenylamine-single-walled carbon nanotube (PTPD–SWCNT) composites enhanced through Lewis acid doping with tris(pentafluorophenyl)borane (BCF). The PTPD polymer disperses SWCNTs effectively, achieving optimal performance at 50 wt% SWCNT loading with a conductivity of 678 S cm⁻¹ and Seebeck coefficient of 28.8 µV K⁻¹. Sequential BCF doping boosts conductivity to 1551 S cm⁻¹ while maintaining thermopower (35 µV K⁻¹ at 428 K), yielding a power factor of 190 µW m⁻¹ K⁻². Spectroscopic analyses confirm hole generation predominantly via Brønsted acid pathways with minor Lewis coordination and Fermi-level modulation that reduces polymer–nanotube interfacial barriers. The composite exhibits excellent thermal stability (T₅ = 575 K after doping) and mechanical flexibility. A flexible seven-leg device generated 0.3 µW at ΔT = 100 K and maintained stable output over 500 bending cycles. This work establishes polytriphenylamine–carbon nanotube composites as a new materials platform for solution-processable, flexible thermoelectric devices for low-grade waste heat harvesting.