Effect of “soft start” i-layer deposition on the performance and stability of a-Si:H p-i-n solar cells

In this study, the authors investigate the effect of an ignition procedure for the i-layer deposition on cell performance and stability. Starting with low RF power (“soft start”), the hydrogen concentration and the defect density at the p-i interface is reduced leading to an increase of the conversion efficiency. This is due to the reduction of particle formation in the discharge and of its detrimental effects on initial film growth under “soft start” conditions. Light soaking experiments performed with solar cells and intrinsic films simultaneously deposited indicate that the relative degradation of the efficiency is mainly determined by the bulk i-layer rather than by the p-i interface region properties. However, due to the increase of efficiency in the initial state, an improvement of the efficiency after degradation could be achieved by this p-i interface optimization