Papers by Author: Wei Ming Lu

Abstract: Hydrogen doped AZO films (HAZO) were prepared by RF magnetron sputtering. A systematic study of the effect of substrate to target distance (Dst) on the structural, electrical and optical properties of the as-grown HAZO films was carried out. Compared with the Al-doped ZnO films, the hydrogen in the atmosphere influenced the growth of the films by incorporating in the films and bombarding the surface of the film, namely, the Dst, which induced the residual stress and the roughness of the films decreased with an increase of the Dst. The films showed a smaller grain size. The surface work function of the films changed with the composition of the films, reaching a maximum at 7.5cm.

Abstract: A novel method to grow silicon dioxide layers for passivating the silicon surface is given more attention. SiO₂ was grown by applying a positive voltage across silicon wafers in a nitric acid solution at low temperature. After annealing in N₂ media at 900°C for 20min, excellent surface passivation was achieved. The maximum effective lifetime of the silicon arrived at 29.8μs and 29.75μs, which was three times the value of silicon without passivation. The effective lifetime of other types of silicon could be ten times the initial value without the silicon dioxide. A comparison study of the effect of the FGA, annealing at low temperature and annealing in N₂ or O₂ containing medium at high temperature were investigated.

Abstract: Texturization of mono-crystalline by chemical anisotropic etching is one of the most important technologies for modern silicon photovoltaic. IPA is usually added to the alkaline etchants to improve the uniformity of the random pyramid texture due to remove hydrogen bubbles sticking on the silicon wafer by improving the wettability of wafer surface. In this investigation, we carried out a systematic study on the influence of IPA concentrations on the textured surface. The etching experiments were performed on (100) silicon wafer in a mixture of 20 vol. % commercial TMAH solutions (10 wt.%) and IPA (rang from 0~12 vol. %) for etching time ranging from 10 to 70 min at 80°C. The etching mechanism in the TMAH solutions with IPA addition was explained basing on the experimental results and the theoretical considerations.

Abstract: Texturing for mono-crystalline silicon solar cell by chemical anisotropic etching is one of the most important techniques in photovoltaic industry. In recent years, tetramethylammonium hydroxide (TMAH) solution or a mixture of TMAH solution with IPA was reported to be used for random pyramids texturization on silicon surface due to its non-volatile, nontoxic, good anisotropic etching characteristics and uncontaminated metal ions. However, most of the studies were reported about the etching processes by using high TMAH concentration solutions. In this study, a simple and cost-effective approach for texturing mono-crystalline silicon wafers in low TMAH concentration solutions was proposed. Etching was performed on (100) silicon wafers using silicon-dissolved tetramethylammonium hydroxide (TMAH) solutions (0.5~1 %) without addition of surfactant. The surface phenomena, surface morphology and surface reflectance have been analyzed. A textured surface with smaller and smooth pyramids can be realized by using 1 % silicon-dissolved TMAH solutions.