Ying-Jie Xing

Field emission analysis of band bending in donor/acceptor heterojunction

The donor/acceptor heterojunction plays an important role in organic solar cells. An investigation of band bending in the donor/acceptor heterojunction is helpful in analysis of the charge transport behavior and for the improvement of the device performance. In this work, we report an approach for detection of band bending in a donor/acceptor heterojunction that has been prepared on a small and sharp tungsten tip. In situ field emission measurements are performed after the deposition process, and a linear Fowler-Nordheim plot is obtained from the fresh organic film surface. The thickness-dependent work function is then measured in the layer-by-layer deposited heterojunction. Several different types of heterojunction (zinc phthalocyanine (ZnPc)/C60, copper phthalocyanine (CuPc)/3,4,9,10-perylenetetracarboxylic bisbenzimidazole, and CuPc/C60) are fabricated and analyzed. The different charge transfer directions in the heterojunctions are distinguished by field emission measurements. The calculation method u...

Improved performance of small molecule solar cell by using oblique deposition technique and zinc phthalocyanine cathode buffer layer

Short circuit current density (Jsc) and open circuit voltage (Voc) are two important parameters to evaluate the performance of organic solar cells. How to increase these two parameters without using novel material still remains a challenge. Two small molecules, zinc phthalocyanine (ZnPc) and 3,4,9,10-perylene tetracarboxylic bisbenzimidazole (PTCBI), are used to fabricate ITO/ZnPc/ZnPc:PTCBI/PTCBI/ZnPc/Al photovoltaic device. We find that Jsc and Voc are enhanced by using oblique deposition technique and ZnPc cathode buffer layer, respectively. Analysis of the active layer reveals phase segregation in obliquely deposited ZnPc:PTCBI bulk heterojunction layer. Field emission measurement is used to probe the band bending and internal field in ZnPc/PTCBI planar heterojunction. The effects of phase segregation and internal field are discussed. This work shows that careful assembly of donor and acceptor material is beneficial to small molecule photovoltaic device.

Mechanical fabrication of carbon nanotube films and their field-emission properties

Summary form only given. We present a simple technology for the fabrication of CNTs films cathode by utilizing method of rubbing CNT powders onto the polished substrates. The metallic substrates were polished by 10000 mesh white fused alumina powder at first. Then, the CNTs were rubbed on them. After that process, the metallic substrates were covered by CNTs films uniformly and firmly, as characterized by scanning electron microscope and scotch tape peeling tests. The field-electron-emission properties of such films cathodes were investigate under the vacuum of 10-5 Pa. The experimental results showed that the field-emission image of the films was nearly uniform and the emission current was considerably large. The turn-on field (the field at an emission current density of 10μA/cm ) was 3.4V/μm. The emission current density of 1.31mA/cm was obtained at the electric field of 6.1 V/μm, and emission current was almost stable in more than 60 minutes under about ImA/cm .