Simultaneously Achieving Green p- and n‑Type Single-Walled Carbon Nanotube Composites by Natural Amino Acids with High Performance for Thermoelectrics

Many drugs, foods, and clothes are derived from natural products; however, little attention has been focused on natural-derived thermoelectric (TE) materials. In this work, several natural amino acids are first introduced to single-walled carbon nanotubes (SWCNTs) and a series of environment-friendly n- and p-type freestanding SWCNT/amino acid films are fabricated as potent TE materials. Among the composites, SWCNT/histidine (His) and SWCNT/lysine (Lys) achieve excellent n-type TE properties, with the highest power factors of 508.5 and 502.0 μW m–1 K–2 at room temperature, respectively. SWCNT/aspartic acid (Asp) displays p-type behaviors, with the highest power factor of 221.6 μW m–1 K–2 at room temperature. Moreover, a TE device based on SWCNT/Lys and SWCNT/Asp including five p–n junctions is fabricated. The high open-circuit voltage (42.3 mV) and output power (4.3 μW) are obtained at ΔT = 87 K. Given the excellent TE performance, green composites based on natural-derived materials can be the promising candidates for TE devices.