Improved Thermal and Electrical Properties of P-I-N-Structured Perovskite Solar Cells Using ZnO-Added PCBM as Electron Transport Layer.

Not only can perovskite solar cells be exposed to high temperatures, up to 80 °C, depending on the operating environment, but absorbed energy is lost as heat, so it is important to have thermal stability for commercialization. However, in the case of the recently reported p-i-n structure solar cell, most of the electron and hole transport layers are composed of organic materials vulnerable to heat transfer, so the light absorption layer may be continuously exposed to high temperatures when the solar cell is operated. In this study, we attempted to improve the thermal conductivity of the electron transport layer using phenyl-C61-butyric acid methyl ester (PCBM) containing zinc oxide (ZnO). As a result, the thermal conductivity was improved by more than 7.4% and 23.5% by adding 6.57vol% and 22.38vol% of ZnO to PCBM, respectively. In addition, the insertion of ZnO resulted in changes in the electron transport behavior and energy level of the electron transport layer. As a result, it was confirmed that not only could the temperature stability of the perovskite thin film be improved, but the efficiency of the solar cell could also be improved from 14.12% to 17.97%.

Synthetic control of the surface area in nickel cobalt oxide for glucose detection via additive-assisted wet chemical method.

We investigated the effect of specific surface area on the electrochemical properties of NiCo2O4 (NCO) for glucose detection. NCO nanomaterials with controlled specific surface areas were prepared by additive-assisted hydrothermal synthesis, and self-assembled nanostructures with urchin-, pine-needle-, tremella-, and flower-like morphologies were obtained. The novelty of this method is the systematic control of chemical reaction routes assisted by the addition of different additives during synthesis, which results in the spontaneous formation of various morphologies without any difference in the crystal structure and chemical states of the constituent elements. Such morphological control of NCO nanomaterials leads to considerable changes in the electrochemical performance for glucose detection. Combined with materials characterization, the relationship between the specific surface area and the electrochemical performance is discussed for glucose detection. This work can provide scientific insights for tailoring the surface area of nanostructures, which determines their functionality for potential applications in glucose biosensors.

Field emission behavior of carbon nanotube yarn for micro-resolution X-ray tube cathode.

Carbon nanotube (CNT) has excellent electrical and thermal conductivity and high aspect ratio for X-ray tube cathode. However, CNT field emission cathode has been shown unstable field emission and short life time due to field evaporation by high current density and detachment by electrostatic force. An alternative approach in this direction is the introduction of CNT yarn, which is a one dimensional assembly of individual carbon nanotubes bonded by the Van der Waals force. Because CNT yarn is composed with many CNTs, CNT yarns are expected to increase current density and life time for X-ray tube applications. In this research, CNT yarn was fabricated by spinning of a super-aligned CNT forest and was characterized for application to an X-ray tube cathode. CNT yarn showed a high field emission current density and a long lifetime of over 450 hours. Applying the CNT yarn field emitter to the X-ray tube cathode, it was possible to obtain micro-scale resolution images. The relationship between the field emission properties and the microstructure evolution was investigated and the unraveling effect of the CNT yarn was discussed.

Fabrication process and electromagnetic wave absorption characterization of a CNT/Ni/epoxy nanocomposite.

Since carbon nanotube (CNT) was first discovered in 1991, it has been considered as a viable type of conductive filler for electromagnetic wave absorption materials in the GHz range. In this paper, pearl-necklace-structure CNT/Ni nano-powders were fabricated by a polyol process as conductive fillers. Compared to synthesized CNT, pearl-necklace Ni-decorated CNT increased the electrical conductivity by an order of 1 due to the enhancement of the Ni-conductive network. Moreover, the decorated Ni particles prevented the agglomeration of CNTs by counterbalancing the Van der Walls interaction between the CNTs. A CNT/Ni nanocomposite showed a homogeneous dispersion in an epoxy-based matrix. This enhanced physical morphology and electrical properties lead to an increase in the loss tangent and reflection loss in the CNT/Ni/Epoxy nanocomposite compared to these characteristics of a CNT/Epoxy nanocomposite in range of 8-12 GHz. The electromagnetic wave absorption properties of CNT/Ni/epoxy nanocomposites will provide enormous opportunities for electronic applications where lightweight EMI shielding or electro-magnetic wave absorption properties are necessary.

Fabrication and characterization of a 3D-structured field emitter using carbon nanotube.

Carbon nanotube has good electrical properties and a high aspect ratio, which enable it to obtain a high current at a low voltage due to its high field. Due to the life and uniformity of their emission tips, carbon nanotube field emitters are hard to commercialize. A field emitter with a three-dimensional (3D) structure was fabricated in this study to overcome such problems. In the 3D-structured field emitter, the field emission tips are located only at the vertical plane, where an enlarged field emission area can be attained. To fabricate the tip of the 3D-structured field emitter, carbon nanotube/silver nanocomposite powders were fabricated via molecular-level mixing and were sprayed at a substrate with good attachment and homogeneous dispersion between the CNT tips and the silver. The field emission properties of the 3D-structured field emitter were then determined and compared with those of a flat field emitter. The field emission area of the 3D-structured field emitter was found to be 4.5 times larger than that of the flat field emitter, with six times higher current density. Moreover, the 3D-structured field emitter had better stability than the flat field emitter. At a high gate field, the emission images of the 3D-structured field emitter showed light spots expanded towards the gate direction.