Manlin Tan

Photovoltaic characteristics of amorphous silicon solar cells using boron doped tetrahedral amorphous carbon films as p-type window materials

Boron doped tetrahedral amorphous carbon (ta-C:B) was prepared by filtered cathodic vacuum arc deposition. A band gap of 2.0eV and a conductivity of 1.42×10−7S∕cm were obtained at the doping ratio of 2.13at.%. A device structure was deduced from the conventional amorphous silicon (a-Si:H) solar cell using the ta-C:B window layer. Photovoltaic parameters of the cells were studied by varying the boron content in the ta-C:B films. A roughly 10% relative improvement of conversion efficiency was observed compared to the normal a-Si:H solar cell. The improved cell performance results from the enhancement of short wavelength response.

Structural Characteristics and Electrode Activities of Phosphorus Incorporated Tetrahedral Amorphous Carbon Films

Studies on structural properties and electrochemical behaviors of conductive phosphorus incorporated tetrahedral amorphous carbon (ta-C:P) films deposited using filtered cathodic vacuum arc technique with PH3 as the dopant source are presently reported. The structural characteristics of the films are characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy. The electrochemical reactivity of ta-C:P films are evaluated by cyclic voltammetry and differential pulse voltammetry. We find that phosphorus implantation enhances the clustering of sp2 sites dispersed in sp3 skeleton, develops the densities of π and π * states and improves the electrical and electrochemical behaviors of the films. It has been established that the inorganic films with amorphous structure appear excellent electrical conductivity and electrochemical activity similar to boron-doped diamond or nitrogen-doped amorphous carbon electrodes. These characteristics demonstrate greatly potential application of ta-C:P films as electrode materials in terms of its large electrochemical potential window, low background current, and a considerable electrochemical activity towards ferricyanide reduction and metal ions analysis.

Influence of Film Thickness on Intrinsic Growth Stress and Raman Evaluation of Tetrahedral Amorphous Carbon Films

To investigate the effects of film thickness on Raman characterization and intrinsic stress of tetrahedral amorphous carbon and ascertain the correlations between stress and Raman spectra, the ta-C films with different film thickness were deposited on the polished P-type (100) c-silicon substrate with the same conditions by the filtered cathodic vacuum arc technology. The film thickness was measured by the surface profiler and the atomic force microscope; stress was calculated according to the curvature of the stress samples examined by the surface profiler; the microstructure of the films was characterized by the Ramanscope. It has been shown that the stress drops down continuously and the dropping rate turns mild with the increase of film thickness. When the film thickness surpasses 30 nm, the compressive stress is kept at less than 5 GPa. The intensity of the first and second order peak of the c-Si substrate in the visible Raman spectra gradually depresses with the increase of thickness. However, the FWHM is minimal and the maximal intensity is highest from 50 nm to 80 nm, accordingly the clearest Raman signals can be acquired in this scale. Additionally, the position of the asymmetric broad peak gradually shifts towards the lower wavenumber with the increase of thickness and the decease of intrinsic stress.