Precise investigation of the light-saturated defect density in amorphous silicon very thin films and solar cells

The authors present progress in the three regions important for optimization of the highest long term a-Si:H solar cells efficiency: (1) in order to achieve light saturated state rapidly and controllably a new method of the accelerated degradation by combined AM1 and pulsed ruby laser illumination is proposed; (2) diagnostic of the degraded state is then made possible by a new constant photocurrent method setup combining standard and transmission modes which gives absorption coefficient a in the absolute units and undisturbed by interferences; (3) the possibility to measure deep defect density of states directly on a-Si:H solar cells by space-charge-limited-current time-of-flight is demonstrated.