Abstract
The hydrogenated microcrystalline silicon(c-Si:H) thin film solar cells can reduce silicon material, and deposited on low-cost substrate like glass, stainless steel or plastics. Therefore it significantly reduce the material cost. The absorption of c-Si:H thin films at near-infrared light is lower, so c-Si:H need thicker film(1~3 m) to enhance absorption. How to increase deposition rate c-Si:H thin films, simultaneously maintain good crystalline volume fraction(XC) and photosensitivity is very importance problem. The free radicals and particles in plasma will affect the material and photoelectric properties of c-Si:H thin films. Thus the correlation between process parameters and properties of films are demonstrated in this thesis. Purpose of this study is develop process for c-Si:H thin films by In-line plasma enhanced chemical vapor deposition(In-line PECVD). The glow of the plasma associated with properties of films is detected by optical emission spectroscopy(OES). The experiment results found that whether it is varying the silane concentration, RF power or gas pressure, the XC increase with OES-ratio(H/SiH*, H/SiH*), and the photosensitivity decrease as OES-ratio increase. It is say that higher hydrogen atom density will increase XC of films, but dark conductivity enhancement also cause photosensitivity decreased. Currently, In-line PECVD can deposited c-Si:H thin film which XC = 38% and photosensitivity = 3.94 × 102 at high power(600 W), high pressure(4 torr) and high silane concentration(2.44%). The N-P layer deposited in ULVAC and c-Si:H I-layer in In-line PECVD, the cell efficiency is 1.68%. But if the N-I-P layer all deposited in In-line PECVD, the cell efficiency achieve 2.27%. From the result, all in In-line PECVD manufacture can prevent air contamination, therefore the cell efficiency can be large improve.