Significantly enhanced thermoelectric performance in SWCNT films via carrier tuning for high power generation

Carbon nanotubes (CNTs) are promising flexible thermoelectric materials in the field of large-scale low-grade thermal energy utilization. However, the relatively poor thermoelectric performance of CNTs near ambient temperature is a big issue for their application as flexible power generator. Here, we improved the thermoelectric properties of SWCNT films in a wide temperature range from room temperature (RT) to 200 °C via facile thermal annealing process. The effects of heat treatment at different temperatures and atmospheres on the thermoelectric properties of SWCNT films were studied. A maximum power factor (PF) of 113.7 μW/m∙K2 at RT is obtained with average PF 111.7 μW/m∙K2 in the RT to 200 °C range, which is more than threefold the value of as-prepared SWCNT film. Flexible and compact power generator based on annealed p-type SWCNT films and n-type polyethylenimine-doped SWCNT films with 8 couples of p-n legs was assembled. An outstanding output power of 1.16 μW with power density of 0.48 W/m2 at temperature difference 49.5 K was achieved. The device showed good air stability within one month and excellent mechanical flexibility. This study thus provides a feasible and low-cost strategy for high power energy generation.