We have developed a highly stabilized hydrogenated amorphous silicon solar cell with extremely low Si-H, bond density in the i layer using a triode-plasma CVD method. Si-H-2 bond density decreased from 1.7 to 0.6 at.%, and correspondingly the degradation ratio of the cell efficiency decreased from 13% to 10% in comparison to the conventional diode system. It was also found that the hydrogen dilution mainly affects Si-H bond density rather than Si-H, bond density in the films. Further optimization for the TCO/p interface results in the stabilized cell efficiency of 9.22%. (c) 2005 Elsevier B.V. All rights reserved.