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Flexible composite films with high power factors are the candidate for wearable energy harvesters, MWCNTs-SnSe/PEDOT:PSS ternary composite films were fabricated by a vacuum filtration method. The effects of cold-pressing on morphology, Raman spectra, and thermoelectric (TE) properties of the composite films were studied. For cold-pressed MSPPD10 ternary composite film, its conductivity and Seebeck coefficient both increase with increasing temperature. The results show that the PF is enhanced to 166.5 μW m−1 K−2 for the cold-pressed MSPPD10 ternary composite film, which is 2.8 times the MSPPD10 (59.35 μW m−1 K−2) composite film without cold-pressing treatment. Besides, the TE property of cold-pressed MSPPD10 ternary composite film is better than that of SnSe or MWCNTs combined with PEDOT:PSS. The cold-pressed MSPPD10 ternary composite film had excellent flexibility, and the resistance only increases 12% after 1000 bends on an iron rod with a radius of 4 mm. In addition, the TE generator consisting of 4-leg cold-pressed MSPPD10 ternary composite films has a maximum output power of 13.5 nW at a temperature gradient of 30 K, showing great potential for flexible TE applications.

In this study, flexible thermoelectric tin selenide (SnSe)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite films have been fabricated by the vacuum filtration method, and their thermoelectric properties were investigated. The electrical conductivities of the composite films have a tendency to decrease with an increase in the SnSe content, while their Seebeck coefficients have an inverse tendency. The electrical conductivities decrease gradually with an increase in temperature, while the Seebeck coefficients show a tendency to increase first and then decrease with the increase in temperature. The maximum power factor (PF = S2σ) of the composite film is obtained when the SnSe content is 10 wt%, which is 24.42 μW m−1 K−2 at 353 K. Besides, the 10 wt% SnSe/PEDOT:PSS film exhibited excellent stability with only a 9% increase in resistance after 1000 bends under a bending radius of 4 mm. When the temperature gradient is 50 K, a flexible thermoelectric generator fabricated by 3 legs of the 10 wt% SnSe/PEDOT:PSS film has an open-circuit voltage and maximum output electrical power of 3.2 mV and 13.73 nW, respectively, which demonstrates a great potential application to power wearable flexible electronic devices.

Flexible multiwall carbon nanotubes (MWCNTs)-10 wt% tin selenide (SnSe)/poly (3,4- ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT: PSS)/5 vol% dimethyl sulfoxide (DMSO) (MSPPD) composite films were fabricated by vacuum filtration method, and their thermoelectric properties were investigated. When the electrical conductivity (σ) and Seebeck coefficient (S) of these composite films with different contents of MWCNTs were measured at different temperatures, σ had an increasing tendency with the increase of MWCNTs content while S would decrease gradually. MWCNTs would improve carrier concentration (n) and mobility (μ) of SnSe/PEDOT: PSS film simultaneously because of MWCNTs with high electrical conductivity and carrier mobility. The maximum power factor PF of 59.35 μWm-1K-2 had been obtained for MSPPD10 composite film at 393 K. The MSPPD10 composite film exhibited ex-cellent flexibility, σ decreased only to 86% of its initial stage after bending 1000 cycles using a rod with a radius of 4 mm. A flexible thermoelectric (TE) generator consisting of 5 legs MSPPD10 could generate an open-circuit voltage of 3.73 mV and maximum output power of 14.74 nW when the temperature gradient was 39 K. This research shows that MWCNTs have great potential to enhance the thermoelectric performance of flexible SnSe/PEDOT: PSS composite films for wearable devices.

The self-supporting and flexible Cu2S/poly(3,4-ethylene dioxythiophene):-poly(styrene sulfonate) (PEDOT:PSS) composite thermoelectric films were prepared by vacuum filtration method. The effects of Cu2S content and the pressure of cold-pressing on the thermoelectric properties of composite films were studied. The electrical conductivities of Cu2S/PEDOT:PSS composite films would decrease with the increase of Cu2S content and temperature, while the Seebeck coefficients had an inverse tendency. At the same time, the electrical conductivities and Seebeck coefficients of the Cu2S/PEDOT:PSS composite films will decrease and increases with the increase of temperature, respectively. The maximum power factor (PF) of composite films was 56.15 μWm-1K-2 when Cu2S content was 10 wt% at 393 K. After cold-pressing at 2 MPa or 4 MPa, the PF of 10 wt% composite film was enhanced by two times. The resistance of the cold-pressed composite film would rise only 10 % after bending 1000 cycles under a bending radius of 4 mm, showing good flexibility. The open-circuit voltage and maximum output power were 2.3 mV and 23.06 nW for the TE generator fabricated by four strips of cold-pressed 10 wt% composite film at the temperature difference of 30 K, respectively, which has a good potential to power the low-power consumption wearable electronic devices.