Carbon nanotube/silicon heterojunctions for photovoltaic applications

Photovoltaic devices have rapidly developed in recent years as they seek to address the ever-increasing energy requirements and environmental issues.Due to their simple structure and easy,low-temperature fabrication,heterojunctions of carbon nanotube(CNT)films and silicon(Si)have been used in solar cells,photodetectors and optoelectronic gas sensors.Significant progress has been made on the development of high-performance CNT/Si heterojunction devices,in particular,CNT/Si solar cells.Here,we give a comprehensive overview of state-of-theart CNT/Si heterojunction devices.The effects of the structure of the CNTs,the interface layer and the silicon structure on the performance of CNT/Si solar cells are analyzed.In addition,potential ways to further improve the performance of such photovoltaic devices are proposed.Finally,the key challenges and developing trends in CNT/Si heterojunction photovoltaic devices are discussed.

Influence of Carbon Nanofiber Addition on Mechanical Properties and Crystallization Behavior of Polypropylene

Carbon nanofiber （CNF）-reinforced polypropylene （CNF/PP） composites with different CNF contents were prepared by melt mixing, and the mechanical properties and crystallization behavior of the CNF/PP composites obtained were investigated. It was found that the tensile modulus of the composites was increased with the addition of CNFs, but their elongation at break and fracture strain energy were decreased, while the tensile strength of the composites was firstly increased and then decreased due to the agglomeration of CNFs at higher loading. Nonisothermal crystallization analysis showed that the CNFs played a role as nucleating agent in PP matrix, which led to increment in the crystallization rate and the degree of crystallinity of PP. Moreover, X-ray diffraction studies showed that the CNFs incorporated in the PP matrix favored the growth of （040）-oriented PP crystals. With the increase in the CNF content, the nucleating and orientation roles of the CNFs were obviously enhanced.

A flexible thermoelectric device based on a Bi_(2)Te_(3)-carbon nanotube hybrid

Thermoelectric(TE)materials and devices have attracted great attention due to their ability to convert waste heat to electrical power and active cooling.However,the conventional bulk TE materials are inorganic semiconductors with inherent brittleness and rigidity.They cannot closely contact curved heat sources and sinks,which limits their application in modern electronics.It remains a big challenge to fabricate high-performance TE materials and devices with good flexibility.Here,we report a flexible TE device comprised of a single wall carbon nanotube(SWCNT)network and(0001)-textured Bi_(2)Te_(3)nanocrystals prepared by a magnetron sputtering technique.The unique Bi_(2)Te_(3)-SWCNT hybrid structure has a TE figure of merit(ZT)value of^0.23 at^330 K.A prototype TE device made of this hybrid gives a maximum output power density of^0.93 m W cm^(-2)under a temperature difference of 25 K at ambient temperature and shows good flexibility under bending.Our results open up a new way to the development of flexible TEs and their application in self-powered portable devices.

Open-pore LiFePO_4/C microspheres with high volumetric energy density for lithium ion batteries

LiFePO4/C microspheres with different surface morphologies and porosities were prepared from different carbon sources. The effects of the surface morphology and pore structure of the microspheres on their electrochemical properties and electrode density were investigated. The electrochemical performance and electrode density depended on the morphology and pore structure of the LiFePO4/C microspheres. Open-pore LiFePO4/C microspheres with rough surfaces exhibited good adhesion with current collectors and a high electrode density （2.6g/cm3）. They also exhibited high performance in a half cell and full battery with a high volumetric energy density.