Janus Helical Ribbon Structure of Ordered Nanowire Films for Flexible Solar Thermoelectric Devices

Abstract

On the other hand, although diverse strategies were successively employed to settle down the thermal dissipation of the cold side, including heat sink, [8,9] appropriate air velocities, [10] and circulation water, [11,12] these methods use rigid and bulky instruments, even leading to dissipate more energy, which increases the cost of large-scale application. Other reported studies cooled the cold side by the latent heat of water evaporation of hydrogel. [13,14] However, it is difficult to keep cooling in a dry environment. Meanwhile, some researchers utilized solar-absorbing substrates to enhance the temperature of the hot side by a dual heat source of waste heat and light. [15,16] Regrettably, the cold sides of STE devices have poor reflectivity to sunlight. Therefore, how to cost-effectively attain desirable ΔT for large-scale implementations is still a challenge.Currently, the passive daytime radiative cooling (PDRC) technique [17][18][19][20] is an emerging and scalable cooling technique, showing encouraging capacity in outdoor cooling fields without extra energy supplements. By taking advantage of the cold space source, the natural but extremely vast heat sink, PDRC materials reflect almost all solar spectrum (wavelength (λ) ≈ 0.28-2.5 µm) to suppress temperature rise in addition to emitting most heat (λ ≈ 8-13 µm) toward the cold space (≈3 K), in which these materials can reach an approximate or even subambient temperature without extra energy input. [21][22][23][24] Thus, increasing thermal dissipation of the cold side will be achieved well via flexible PDRC thin films. At the same time, for the larger ΔT across STE legs, Solar thermoelectric devices play a significant role in addressing the problem of global warming, owing to their unique features of converting both waste heat and solar energy directly into electricity. Herein, a flexible 3D Janus helical ribbon architecture is designed, starting from well-aligned tellurium (Te) nanowire film, using an in situ redox process reacting with Ag + and Cu 2+ resulting in n-type, p-type, and photothermal sides in one film. Remarkably, the device shows all-day electricity generation and large temperature gradient by coupling the cold side with a passive radiative cooling technique and the hot side with a selective solar absorption technique, showing a temperature gradient of 29.5 K, which is much higher than previously reported devices under a low solar radiation of only 614 W m −2 . Especially, the device can still generate electricity even at night. The present strategy offers a new way for heat management by efficiently utilizing solar energy and the cold of the universe.

Advances in photothermal regulation strategies: from efficient solar heating to daytime passive cooling

“…33g). 534 The Janus helical ribbon structure in the solar thermoelectric (STE) achieves efficient heat management on both hot and cold sides, leading to excellent electricity generation potential by their large Δ T of 29.5 °C under a solar irradiance of 614 W m −2 . Furthermore, apart from the sunlight, the STE can generate electricity when the hot side is attached to a heating panel that can generate similar industrial waste heat.…”

An Emerging Energy Technology: Self‐Uninterrupted Electricity Power Harvesting from the Sun and Cold Space

“…[32] Figure 6h shows a flexible 3D Janus helical ribbon device with n-type, p-type thermoelectric element, and photothermal layers in one film and couple with a radiative cooler. [102] Additional mirrors can be used to alter the optical path so that the sunlight shines directly at the bottom of the power generation system (Figure 6i), reducing the adverse effect of the shielding on heat transfer at the solar heating end. In this case, the thermal energy in the system flows completely from bottom to top, minimizing the amount of heat escaping from the side.…”

“…The photothermal conversion performance of the solar absorber and the cooling performance of the radiative cooler have approached the theoretical limit, and the manufacturing technology of thermoelectric materials and devices has also made exciting progress. [102][103][104][105][106] The combination of sky-facing radiative cooler and solar absorber with thermoelectric generator is a new energy device that is easy to implement but has greater parasitic heat loss. The non-planar thermoelectric device integrated with solar heating and radiative cooling can be coupled with a variety of functional devices and environmental heat sources to improve its output performance and enrich its application scenarios, but it has a more complex manufacturing process and needs to consider the path of solar radiation and thermal radiation to reduce the shielding effect.…”

High Efficiency Breathable Thermoelectric Skin Using Multimode Radiative Cooling/Solar Heating Assisted Large Thermal Gradient

“…Despite the favorable Janus helical structure to widen the thermal differential, the device does not offer wearability and thus cannot be practically applied to the on-skin electronics. [31] For the wTEG to be practically applied to the on-skin electronics, it must attain certain properties: 1) stretchability and mechanical conformability that enable intimate contact with deformable human skin to achieve both high wear comfort and maximized heat transfer, and 2) biocompatibility and breathability that allow sweat evaporation and gas exchange. These characteristics induce comfortable sensations even with prolonged use of wearable electronics.…”