Synergistic Dual Doping of Sulfur and Copper for Improved Thermoelectric Properties of Silver Selenide Nanomaterials.

Research on flexible thermoelectric (TE) materials has typically focused on conducting polymers and conducting polymer-based composites. However, achieving TE properties comparable in magnitude to those exhibited by their inorganic counterparts remains a formidable challenge. This study focuses on the synthesis of silver selenide (Ag2 Se) nanomaterials using solvothermal methods and demonstrates a significant enhancement in their TE properties through the synergistic dual doping of sulfur and copper. Flexible TE thin films demonstrating excellent flexibility are successfully fabricated using vacuum filtration and hot-pressing techniques. The resulting thin films also exhibited outstanding TE performance, with a high Seebeck coefficient (S = -138.5 µV K-1 ) and electrical conductivity (σ = 1.19 × 105  S m-1 ). The record power factor of 2296.8 µW m-1  K-2 at room temperature is primarily attributed to enhanced carrier transport and interfacial energy filtration effects in the composite material. Capitalizing on these excellent TE properties, the maximum power output of flexible TE devices reached 1.13 µW with a temperature difference of 28.6 K. This study demonstrates the potential of Ag2 Se-based TE materials for flexible and efficient energy-harvesting applications.

Correction: A three-dimensional metal grid mesh as a practical alternative to ITO.

Correction for 'A three-dimensional metal grid mesh as a practical alternative to ITO' by Sungwoo Jang et al., Nanoscale, 2016, 8, 14257-14263.

Foldable Thermoelectric Materials: Improvement of the Thermoelectric Performance of Directly Spun CNT Webs by Individual Control of Electrical and Thermal Conductivity.

We suggest the fabrication of foldable thermoelectric (TE) materials by embedding conducting polymers into Au-doped CNT webs. The CNT bundles, which are interconnected by a direct spinning method to form 3D networks without interfacial contact resistance, provide both high electrical conductivity and high carrier mobility. The ZT value of the spun CNT web is significantly enhanced through two simple processes. Decorating the porous CNT webs with Au nanoparticles increases the electrical conductivity, resulting in an optimal ZT of 0.163, which represents a more than 2-fold improvement compared to the ZT of pristine CNT webs (0.079). After decoration, polyaniline (PANI) is integrated into the Au-doped CNT webs both to improve the Seebeck coefficient by an energy-filtering effect and to decrease the thermal conductivity by the phonon-scattering effect. This leads to a ZT of 0.203, which is one of the highest ZT values reported for organic TE materials. Moreover, Au-doped CNT/PANI web is ultralightweight, free-standing, thermally stable, and mechanically robust, which makes it a viable candidate for a hybrid TE conversion device for wearable electronics. When a 20 K temperature gradient is applied to the TE module consisting of seven p-n couples, 1.74 µW of power is generated.

A three-dimensional metal grid mesh as a practical alternative to ITO.

The development of a practical alternative to indium tin oxide (ITO) is one of the most important issues in flexible optoelectronics. In spite of recent progress in this field, existing approaches to prepare transparent electrodes do not satisfy all of their essential requirements. Here, we present a new substrate-embedded tall (∼350 nm) and thin (∼30 nm) three-dimensional (3D) metal grid mesh structure with a large area, which is prepared via secondary sputtering. This structure satisfies most of the essential requirements of transparent electrodes for practical applications in future opto-electronics: excellent optoelectronic performance (a sheet resistance of 9.8 Ω□(-1) with a transmittance of 85.2%), high stretchability (no significant change in resistance for applied strains <15%), a sub-micrometer mesh period, a flat surface (a root mean square roughness of approximately 5 nm), no haze (approximately 0.5%), and strong adhesion to polymer substrates (it survives attempted detachment with 3M Scotch tape). Such outstanding properties are attributed to the unique substrate-embedded 3D structure of the electrode, which can be obtained with a high aspect ratio and in high resolution over large areas with a simple process. As a demonstration of its suitability for practical applications, our transparent electrode was successfully tested in a flexible touch screen panel. We believe that our approach opens up new practical applications in wearable electronics.

High-performance of PEDOT/PSS free organic solar cells on an air-plasma-treated ITO substrate.

In this work, we demonstrate the high-performance of a PEDOT:PSS free organic photovoltaic cell (OPVC) using an air-plasma modified ITO surface, followed by controlled solvent evaporation and annealing of the P3HT:PCBM photoactive layer. Ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and conductive atomic force microscopy (c-AFM) results show that the work function of ITO was increased to as high as that of PEDOT:PSS (5.2 eV) after air-plasma treatment, along with significantly enhanced electrical homogeneity. From the dynamic secondary ion mass spectroscopy (DSIMS) results, we confirm that the thermodynamic stability of the slow-dried active layer is attributed to the uniform vertical compositional distribution on the air plasma treated ITO surface, even after thermal annealing at 150 °C for 10 min. The resulting device has an open-circuit voltage of 0.65 V, a fill factor of 63%, and a power conversion efficiency of 3.38%, providing a high performance PEDOT:PSS free OPVC device.

Highly efficient top-illuminated flexible polymer solar cells with a nanopatterned 3D microresonant cavity.

Top-illuminated flexible polymer solar cells with 3D micoresonant cavity provide not only powerful light-trapping but also electrical enhancement, resulting in significant enhancement of power efficiency (26.4%). Capping layer (CL) enhanced the transmittance of the transparent electrodes, increasing electric field intensity in the photoactive layer by forming microresonant cavity, and the nano-pattern on the rear electrodes caused significant enhancement to the Jsc by improving light absorption and charge collection.