Dexian Zhang

Influence of the gas flow of Argon and the distance between substrate and plasma on properties of Al-doped zinc oxide films

Al-doped ZnO(ZAO) films were deposited by DC magnetron sputtering using facing zinc oxide targets at room temperature and in argon atmosphere. The effects of the gas flow of Argon and the distance between substrate and plasma on the properties of the ZAO thin films were characterized by several techniques. By optimizing the craft of preparation, the electrical resistivity as low as 3.3×10-4 Ω·cm and the optical transmittance over 80% in the visible range were obtained for these thin ZAO films. Therefore, the ZAO thin films were suitable for the window layers of n-i-p thin film solar cells or transparent conductive films.

Boron doped hydrogenated nanocrystalline silicon thin films prepared by layer-by-layer technique and its application in n-i-p flexible amorphous silicon thin film solar cells

Boron doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films are deposited using layer-by-layer technique in radio frequency (RF) plasma enhance chemical vapor deposition system. Studies about the influence of gas pressure, RF power density and buffer layer in i/p interface on the microstructure and electrical properties of Boron doped nc-Si:H thin films have been carried out. The experimental results have shown that a), as the gas pressure decreases, the grain size of nc-Si:H thin film increases, while its conductivity turns small, and the thin films transform into amorphous silicon when the gas pressure decreases to 100Pa; b), the microstructure of nc-Si:H thin films evolves to more ordered when the power density was enhanced from 280mW/cm2 to 560mW/cm2, and the grain size changes to be larger; c), the thickness of i/p buffer has large effect on the microstructure of Si:H thin films, when the deposition time of buffer layer increases from 0min to 10min, the Si:H thin films changes from amorphous to nanocrystalline, however the optimal time is about 2min. When the boron doped nc-Si:H thin films are applied as the window layer of n-i-p flexible amorphous silicon solar cells, comparing with p type a-SiC:H window layer, the performance of solar cells have been largely improved.

Study of stability for a-Si:H thin-film solar cells on polyimide substrates

Hydrogenated amorphous silicon thin film solar cells are prepared using radio frequency plasma enhanced chemical vapor deposition on polyimide substrates. The structure of the cell is polyimide /Al/n-μc-Si:H/i-a-Si:H/p-a-SiC:H/TCO. Due to amorphous silicon cells have Staebler-Wronski effect and their efficiencies do not stabilize at prepared, so these cells were placed more than fifteen months and I-V characteristics of these cells were measured in four times. They include (i)in the initial, (ii) placed in desiccator over fifteen months, (iii) light-soaked for five hours under AM 1.5 (100mW/cm2) and (iv) annealed for two hours in natural conditions. The measurement results such as open-circuit voltage, short-circuit current, resistance in series, parallel resistance, conversion efficiency and fill factor are given and studied. Staebler-Wronski Effect are found and explained with these parameters. Generally, after light-soaking, the short-circuit currents of cells increase, the fill factors and open-circuit voltage decrease and the reduction of the efficiency is proportional to the fill factor. Abnormal Staebler-Wronski Effect appears in a cell. The cause of these phenomena is analyzed. The consequence that the efficiency varieties with the fill factor is derived r. A graded gap in P-I interface can be improved the cell efficiently. Ultimately, the stability of a-SiH thin film solar cells on polyimide substrate is discussed.