Fei Jiao

Flexible thin films of poly(nickel-ethylenetetrathiolate) prepared by an electrochemical method display promising n-type thermoelectric properties with the highest ZT value up to 0.3 at room temperature. Coexistence of high electrical conductivity and high Seebeck coefficient in this coordination polymer is attributed to its degenerate narrow-bandgap semiconductor behavior.

Organic photothermoelectric (PTE) materials are promising candidates for various photo-detection applications. Herein, we report on poly[Cux(Cu-ett)]:PVDF, which is an excellent polymeric thermoelectric composite, possesses unprecedented PTE properties. The NIR light irradiation on the poly[Cux(Cu-ett)]:PVDF film could induce obvious enhancement in Seebeck coefficient from 52±1.5 to 79±5.0 V/K. By taking advantage of prominent photo-thermoelectric effect of poly[Cux(Cu-ett)]:PVDF, an unprecedented voltage of 12 mV was obtained. This excellent performance enables its promising applications in electricity generation from solar energy and NIR detection to a wide range of light intensities ranging from 1.7 mW/cm2 to 17 W/cm2.

ABSTRACT A kind of bulk organic thermoelectric material namely Cu(I)-ethylenetetrathiolate was synthesized, and its thermoelectric properties were optimized using chemical oxidation and reduction. Both X-ray absorption fine structure and X-ray photoelectron spectroscopy techniques were used to characterize the complex. The material showed p-type property and the best thermoelectric properties were achieved with a power factor of 118.2 mu Wm(-1) K-2 and a ZT of 0.060 at 400K. A thermogenerator based on this material and n-type poly[K-x(Ni-ethylenetetrathiolate)] had an open voltage of 1.51 V and a short current of 2.71 mA under a temperature difference of 60 K. The maximum power output exceeded 1 mW, which is the best performance of the thermoelectric modules based on organic thermoelectric materials. The thermogenerator could power a liquid crystal display calculator, which shed light on the practical use of organic thermoelectric materials.

An unusual wurtzite phase of Cu2ZnGeSe4 (CZGSe) has been discovered and its corresponding nanocrystals (NCs) were synthesized by using a facile hot-injection solution-phase synthesis method. Moreover, the formation mechanism of this new phase of CZGSe, instead of the typically observed stannite structure, has been investigated in detail, which indicates that wurtzite CZGSe, which represents the kinetic phase, could be prepared by using a kinetic growth process without phase transformation into the thermodynamically stable stannite structure during the colloidal synthesis. In addition, the potential of wurtzite CZGSe as a thermoelectric material is demonstrated by characterizing the thermoelectric properties of as-synthesized wurtzite CZGSe NCs. This work allows for a rational manipulation of the NCs with a desired crystal structure through adjusting the thermodynamics and kinetics without using any additives and, because of its simplicity and versatility, it may be extended to the phase-controlled synthesis of other chalcogenide NCs.

Solar photovoltaic technologies could fully deploy and impact the energy conversion systems in our society if mass-produced energy-storage solu-tions exist. A supercapacitor can regulate the fluctuations on the electrical grid on short time scales. Their mass-implementation requires the use of abundant materials, biological and organic synthetic materials are attrac-tive because of atomic element abundancy and low-temperature synthetic processes. Nanofibrillated cellulose (NFC) coming from the forest industry is exploited as a three-dimensional template to control the transport of ions in an electrolyte-separator, with nanochannels filled of aqueous electrolyte. The nanochannels are defined by voids in the nanocomposite made of NFC and the proton transporting polymer polystyrene sulfonic acid PSSH. The ionic conductivity of NFC-PSSH composites (0.2 S cm–1  at 100% relative humidity) exceeds sea water in a material that is solid, feel dry to the finger, but filled of nanodomains of water. A paper-based supercapacitor made of NFC-PSSH electrolyte-separator sandwiched between two paper-based elec-trodes is demonstrated. Although modest specific capacitance (81.3 F g–1), power density (2040 W kg–1) and energy density (1016 Wh kg–1), this is the first conceptual demonstration of a supercapacitor based on cellulose in each part of the device; which motivates the search for using paper manufac-turing as mass-production of energy-storage devices.

Ionic thermoelectric materials, for example, polyelectrolytes such as polystyrene sulfonate sodium (PSSNa), constitute a new class of materials which are attracting interest because of their large Seebeck coefficient and the possibility that they could be used in ionic thermoelectric SCs (ITESCs) and field effect transistors. However, pure polyelectrolyte membranes are not robust or flexible. In this paper, the preparation of ionic thermoelectric paper using a simple, scalable and cost-effective method is described. After a composite was fabricated with nanofibrillated cellulose (NFC), the resulting NFC–PSSNa paper is flexible and mechanically robust, which is desirable if it is to be used in roll-to-roll processes. The robust NFC– PSSNa thermoelectric paper combines high ionic conductivity (9 mS cm À1), high ionic Seebeck coefficient (8.4 mV K À1) and low thermal conductivity (0.75 W m À1 K À1) at 100% relative humidity, resulting in overall figure-of-merit of 0.025 at room temperature which is slightly better than that for the PSSNa alone. Fabricating a composite with cellulose enables flexibility and robustness and this is an advance which will enable future scaling up the manufacturing of ITESCs, but also enables its use for new applications for conformable thermoelectric devices and flexible electronics.

Ultrathin carbon films were prepared by carbonization of a solution processed polyacrylonitrile (PAN) film in a moderate temperature range (500–700 °C). The films displayed balanced hole (0.50 cm2 V−1 s−1) and electron mobilities (0.20 cm2 V−1 s−1) under ambient conditions. Spectral characterization revealed that the electrical transport is due to the formation of sp2 hybridized carbon during the carbonization process. A CMOS-like inverter demonstrated the potential application of this material in the area of carbon electronics, considering its processability and low-cost.

The evolution of the society is characterized by an increasing flow of information from things to the internet. Sensors have become the cornerstone of the internet-of-everything as they track various parameters in the society and send them to the cloud for analysis, forecast, or learning. With the many para meters to sense, sensors are becoming complex and difficult to manufacture. To reduce the complexity of manufacturing, one can instead create advanced functional materials that react to multiple stimuli. To this end, conducting polymer aerogels are promising materials as they combine elasticity and sensitivity to pressure and temperature. However, the challenge is to read independently pressure and temperature output signals without cross-talk. Here, a strategy to fully decouple temperature and pressure reading in a dual-parameter sensor based on thermo-electric polymer aerogels is demonstrated. It is found that aerogels made of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) can display properties of semiconductors lying at the transition between insulator and semimetal upon exposure to high boiling point polar solvents, such as dimethylsulfoxide (DMSO). Importantly, because of the temperature-independent charge transport observed for DMSO-treated PEDOT-based aerogel, a decoupled pressure and temperature sensing can be achieved without cross-talk in the dual-parameter sensor devices.

In this article, we put forward a simple method for the synthesis of thermoelectric (TE) composite materials. Both n- and p-type composites were obtained by ball-milling the insoluble and infusible metal coordination polymers with other polymer solutions. The particle size, film morphology and composition were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The TE properties of the drop-cast composite film were measured at different temperatures. An inkjet-printed flexible device was fabricated and the output voltage and short-circuit current at various hot-side temperatures (Thot) and temperature gradients (ΔT) were tested. The composite material not only highly maintained the TE properties of the pristine material but also greatly improved its processability. This method can be extended to other insoluble and infusible TE materials for solution-processed flexible TE devices.