Near infrared photothermoelectric effect in transparent AZO/ITO/Ag/ITO thin films

Achieving Free-Standing PEDOT:PSS Solar Generators with Efficient All-in-One Photothermoelectric Conversion

Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has attracted widespread attention in solar generation due to its unique all-in-one photothermoelectric effect. However, the poor photothermal conversion, low conductivity, and unsatisfied mechanical properties limit its practical application. Herein, ionic liquids (IL) were first used to improve the conductivity of PEDOT:PSS through ion exchange, then surface-charged nanoparticles SiO₂-NH₂ (SiO₂⁺) were added to promote the dispersion of IL and as a thermal insulator to decrease thermal conductivity. It resulted in a largely enhanced electrical conductivity and decreased thermal conductivity of PEDOT:PSS simultaneously. The obtained PEDOT:PSS/Ionic Liquid/SiO₂⁺ (P_IL_SiO₂⁺) film generated an excellent photothermal conversion of 46.15 °C, which improved ∼134 and ∼82.3% compared with PEDOT:PSS and PEDOT:PSS/Ionic Liquid (P_IL) composites, respectively. In addition, the thermoelectric performance increased by ∼270% more than P_IL films. As a result, the photothermoelectric effect for the self-supported three-arm devices produced an enormous output current and power of ∼50 μA and 13.57 nW, respectively, which showed significant improvement compared with other PEDOT:PSS films reported in the literature. Furthermore, the devices demonstrated outstanding stability with an internal resistance variation of less than 5% after 2000 cycles of bending. Our research offered significant insights into the flexible, high-performance, all-in-one photothermoelectric integration.

Mid-infrared circular-polarization-sensitive photodetector based on a chiral metasurface with a photothermoelectric effect

Photothermoelectric conversion in chiral metasurfaces with thermoelectric material provides an effective way to achieve circular polarization recognition. In this paper, we propose a circular-polarization-sensitive photodetector in a mid-infrared region, which is mainly composed of an asymmetric silicon grating, a film of gold (Au), and the thermoelectric B i ₂ T e ₃ layer. The asymmetric silicon grating with the Au layer achieves high circular dichroism absorption due to a lack of mirror symmetry, which results in a different temperature increasing on the surface of the B i ₂ T e ₃ layer under right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) excitation. Then the chiral Seebeck voltage and output power density are obtained, thanks to the thermoelectric effect of B i ₂ T e ₃. All the works are based on the finite element method, and the simulation results are conducted by the Wave Optics module of COMSOL, which is coupled with the Heat Transfer module and Thermoelectric module of COMSOL. When the incident flux is 1.0W/c m ², the output power density under RCP (LCP) light reaches 0.96m W/c m ² (0.01m W/c m ²) at a resonant wavelength, which achieves a high capability of detecting circular polarization. Besides, the proposed structure shows a faster response time than that of other plasmonic photodetectors. Our design provides a novel, to the best of our knowledge, method for chiral imaging, chiral molecular detection, and so on.

All-optical AZO-based modulator topped with Si metasurfaces

All-optical communication systems are under continuous development to address different core elements of inconvenience. Here, we numerically investigate an all-optical modulator, realizing a highly efficient modulation depth of 22 dB and a low insertion loss of 0.32 dB. The tunable optical element of the proposed modulator is a layer of Al-doped Zinc Oxide (AZO), also known as an epsilon-near-zero transparent conductive oxide. Sandwiching the AZO layer between a carefully designed distributed Bragg reflector and a dielectric metasurface-i.e., composed of a two-dimensional periodic array of cubic Si-provides a guided-mode resonance at the OFF state of the modulator, preventing the incident signal reflection at λ = 1310 nm. We demonstrate the required pump fluence for switching between the ON/OFF states of the designed modulator is about a few milli-Joules per cm². The unique properties of the AZO layer, along with the engineered dielectric metasurface above it, change the reflection from 1 to 93%, helping design better experimental configurations for the next-generation all-optical communication systems.