Kinetics of defects and electron, hole diffusion lengths during light soaking and consequent annealing

Light induced degradation of electronic properties observed in amorphous si licon (a-Si:H) still remains a debated problem. Photoinduced defects are mo stly studied in amorphous silicon films, while less is known about light in duced changes of electron and hole diffusion lengths which are important pa rameters affecting the performance of solar cells. We present data on the k inetics of the recovery of the conductivity, the defect density, and the el ectron and hole diffusion lengths in amorphous silicon films in their light soaked state. Defect density, electron and hole diffusion lengths were mea sured by constant photocurrent method (CPM), and dynamic interference grati ng (DIG) method, respectively. We found that in contrast to light-soaking, the annealing kinetics of electron and hole diffusion lengths are similar a nd correlated to the annealing kinetics of the defect density. Kinetic coef ficients of photo- and thermal-generation and annealing of defects were cal culated from evolution of the defect density. Data on kinetics of defects d uring both annealing and light soaking were treated in the frame of two-wel l model. (C) 2000 Elsevier Science B.V. All rights reserved.