Constructing A/B-Side Heterogeneous Asynchronous Structure with Ag₂Se Layers and Bushy-like PPy toward High-Performance Flexible Photo-Thermoelectric Generators

Abstract

The enthusiasm for environmental energy harvesting has triggered a boom in research on photo-thermoelectric generators (PTEGs), and the relevant applications are mainly focused on self-energy supply sensors owing to the limitations of their output performances. For this purpose, high-output hierarchical heterogeneous PTEGs were constructed by assembling separately optimized thermoelectric (TE) and photothermal (PT) layers. The pressure and temperature conditions of Ag2Se films during the pressing process were first explored, and the sample with the optimal performance and least defects was selected as the TE layer. At the same time, different morphologies of polypyrrole (PPy) PT layers were electrochemically synthesized. It is found that the three-dimensional structure of Bushy-PPy could effectively improve the light absorption and thus enhance the PT conversion performance. The final assembled PTEG can produce an output voltage of −9.03 mV and an output power of 3.53 μW under the irradiation of a near-infrared light source of 300 mW cm–2 without a cooling source, and it can also achieve considerable output power under visible light irradiation of different intensities. Combining its high retentions of electrical conductivity (99%) and output performance (97%) after 1000 bending-tension cycles, it is proven to be a promising next-generation wearable flexible energy harvesting device.

Ag2Se/nylon self-supporting composite films for wearable photo-thermoelectric generators with high output characteristics

“…S10 †) that the Ag 2 Se grain structures on the bers have been signicantly transformed from the original loose irregular crystals into dense bulk crystals, which is similar to the transformation of Ag 2 Se from one-dimensional crystals to bulk crystals in the previously reported hot-pressed non-self-supporting Ag 2 Se lms and will greatly improve their carrier transport properties. 15,43 It can also be noticed that the crystal sizes of Ag 2 Se in the hot-pressed lms are mostly below 1 mm. A smaller grain size usually leads to a decrease in phonon thermal conductivity, which in turn must be benecial to the reduction of the overall thermal conductivity of the sample.…”

“…Generally speaking, there are many factors affecting the PT effect of materials, such as absorbance, surface topography, thermal conductivity of materials, etc. 43 For metals such as gold and silver, on the one hand, the effective local surface plasmon resonance can only be triggered by some nanostructures (nanoparticles, nanorods, etc. ) to generate PT properties, 53–55 on the other hand, the extremely high thermal conductivity of sliver will make the produced heat dissipate quickly, so a poor PT effect is exhibited by the Ag/nylon composite film.…”

“…Meanwhile, the extremely high light transmission (over 90%) of the PDMS layer will not have a significant impact on the PT characteristics of the composite films. 43 Fig. 5c illustrates the open-circuit output voltage (OCV) generated when the PTEG is irradiated at one end with different intensities of 808 nm NIR light.…”

“…In previous work, we have demonstrated that the adoption of high transmittance PDMS packaging can avoid oxidation with little reduction in PT effects, so the PDMS layer was continued to be utilized in this work. 43 During the measurement, one side (about one-half of the sample) of several strips was irradiated with NIR light (LSR808H-FC-5W, LASEVER Inc., China), visible light from a xenon lamp AM 1.5 filter (HSX-F300, NBet Inc., China) and real sunlight (solar altitude angle 76°, Chengdu, China) to obtain the related output characteristics of the device, and the other side was covered with aluminum foil to avoid exposure to light. At the same time, a series of output characteristics of the device were recorded using a multimeter system (Keithley DAQ6510, Tektronix Inc., USA).…”

“…For instance, a heterogeneous asynchronous PTEG was obtained in our previous study by optimizing the non-self-supporting Ag 2 Se TE layer and the polypyrrole (PPy) PT layer, respectively. 43 The perfect crystal structure of Ag 2 Se and Bushy-PPy contribute to the excellent output characteristics of the device together. However, on the one hand, the macroscopic interface between the PT and TE layers in this structure leads to the loss of heat, 42 and on the other hand, the construction of additional PT layers requires complicated process steps, which is not favorable for series production.…”