The Characteristic of amorphous silicon solar cells have been analysed by a numerical analysis. A computer simulation program is proposed for the analysis. The ZnO/nip/metal structure is used basically and other structural effects are also analysed. The rear undoped a-SiC layer of $\delta$-doped p layer is to be thickened sufficiently($200\sim300\mbox{\AA}$) for high open circuit voltage. The rear graded bandgap buffer layer between p and i layer raises effectively open circuit voltage by reducing p-i interface recombination rate. The ZnO between p layer and metal substrate raises short circuit current dramatically by the back scattering, and i layer can be shortened($\sim2500\mbox{\AA}$) as the result. In the next, the wide bandgap $\mu$c-n material was substituted for normal a-Si : H n material and it raises short circuit current by improving the collection efficiency of the short wavelength range(300$\sim$ 550 nm). In the conclusion, the ZnO/$\mu$c-n/buffer/i/buffer/p/ZnO/metal sandwich structure amorphous silicon solar cell which has high efficiency($\sim$ 13\%) is proposed in this paper.
