Jinbo Pang

Effect of substrate temperature on the structural and electrical properties of CIGS films based on the one-stage co-evaporation process

Cu(In, Ga)Se2 thin films were deposited on Mo/soda-lime glass substrates by the one-stage co-evaporation process at the substrate temperatures (Tsub) from 350 °C to 550 °C. The structural and electrical properties of CIGS films have been studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall effect measurement. The experimental results indicate that a temperature of 450 °C is critical for CIGS films grown by the one-stage process. The (In, Ga)2Se3 phase with high resistivity is found below this temperature. The higher Tsub will lead to the formation of single-phase CIGS films with larger grain size and better electrical properties. A higher carrier concentration and lower resistivity of CIGS films are ascribed to sodium incorporation diffused from the glass substrate and the disappearance of the (In, Ga)2Se3 phase in CIGS films. Additionally, the performance of the CIGS solar cells improves significantly with the increase of Tsub. It can be attributed to the reduction of the grain-boundary recombination and the sufficient reaction between the additional (In, Ga)2Se3 phase and the CuxSey binary phase at Tsub above 500 °C.

CVD growth of 1D and 2D sp 2 carbon nanomaterials

The discovery of graphene and carbon nanotubes (rolled-up graphene) has excited the world because their extraordinary properties promise tremendous developments in many areas. Like any materials with application potential, it needs to be fabricated in an economically viable manner and at the same time provides the necessary quality for relevant applications. Graphene and carbon nanotubes are no exception to this. In both cases, chemical vapor deposition (CVD) has emerged as the dominant synthesis route since it is already a well-established process both in industry and laboratories. In this work, we review the CVD fabrication of graphene and carbon nanotubes. Initially, we briefly introduce the materials and the CVD process. We then discuss pretreatment steps prior to the CVD reaction. The discussion then switches to the CVD process, provides comparative data for thermal CVD and plasma-enhanced CVD, and includes coverage of kinetics, thermodynamics, catalyst choice, and other aspects of growth as well as post production treatments. Finally, conclusions are drawn and presented.

Effect of Na on lower open circuit voltage of flexible CIGS thin-film solar cells prepared by the low-temperature process

In this work, we deposit the chalcopyrite semiconductor CuInxGa1-xSe2 (CIGS) thin films using a three-stage co-evaporation process below 450 °C. It is observed that when the soda-lime glass substrate is replaced by polyimide, the conversion efficiency of this CIGS device changes from 11.12% down to 9.1%, and this efficiency decrease results mainly from the different open-circuit voltage (Voc). Temperature-dependent current–voltage measurements are carried out, from which the activation energy is extracted; furthermore, the dominant recombination mechanisms as well as paths are determined, and finally the reason for the different Voc is analyzed.

Direct synthesis of graphene from adsorbed organic solvent molecules over copper

The isolation of graphene by Novoselov et al. in 2004 ignited massive interest in this material. For graphene to succeed fully as a future material its controlled fabrication is required. While numerous routes have been and are being developed, chemical vapor deposition (CVD) is by far the most common approach. There is also interest in forming graphene directly from adsorbed molecules on a substrate. Few examples exist and those that do require multiple steps and rarely offer large graphene domains. In this work we demonstrate a remarkably simple route in which organic solvent precursor molecules are heated in a hydrogen rich atmosphere to directly form graphene over clean Cu foils. The single-step synthesis route has been studied systematically. The systematic studies not only highlight the importance of hydrogen radicals for this reaction, but also provide improved understanding of the role of hydrogen in the formation of graphene from hydrocarbon precursors (e.g. graphene fabrication from thermal CVD).

Accurate Line Detection by Adjusting Hough Transform Threshold Adaptively

An improved image tracking algorithm, PCA tracking algorithm combined with adaptive Kalman filter, is proposed in the paper. The algorithm is used to track targets in image sequences. The PCA tracking algorithm is used to initialize the Kalman filter, and the prediction value is used as the search center of the PCA tracking algorithm. Loop this process to track targets in the image sequence. The targats can be followed very well, for the adaptive Kalman filter is used to predict the trajectory of the object . The PCA tracking algorithm is based on the edge structure, hence when the image gray of the target and background is mixed into one, the targets can be marked. The simulation results show that the algorithm has good capacity to follow the target and has good anti-noise and anti-degradation ability.