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

Light induced degradation of electronic properties observed in amorphous silicon (a-Si:H) still remains a debated problem. Photoinduced defects are mostly studied in amorphous silicon films, while less is known about light induced changes of electron and hole diffusion lengths which are important parameters affecting the performance of solar cells. We present data on the kinetics of the recovery of the conductivity, the defect density, and the electron and hole diffusion lengths in amorphous silicon films in their light soaked state. Defect density, electron and hole diffusion lengths were measured by constant photocurrent method (CPM), and dynamic interference grating (DIG) method, respectively. We found that in contrast to light-soaking, the annealing kinetics of electron and hole diffusion lengths are similar and correlated to the annealing kinetics of the defect density. Kinetic coefficients of photo- and thermal-generation and annealing of defects were calculated from evolution of the defect density. Data on kinetics of defects during both annealing and light soaking were treated in the frame of two-well model.