Experimental and Computer Modelling Studies of Metastability of Amorphous Silicon Based Solar Cells

Abstract

We present a combination of experimental and computer modelling studies of the light induced degradation in the performance of amorphous silicon based single junction solar cells. Of particular interest in this study is the degradation kinetics of different types of amorphous silicon single junction solar cells and the role of dangling bond states in mediating or driving the degradation mechanism. The approach taken in this study has enabled has to examine how light induced degradation is affected by both the structural and material improvement. The study encompasses the application of the microscopic models describing the creation and distribution of midgap defect states to numerical simulation of the as-deposited and degraded states of a solar cell. We have developed computer modeling schemes for simulating the degraded state of amorphous silicon solar cells taking into account the nature and distributions of dangling bond states during illumination. The results of our simulations are in good agreement with the experimentally observed increase in the dangling bond density of states during illumination. Although there is still an uncertainty in the microscopic processes occurring in amorphous silicon during illumination, with the methods developed in this study, it is possible to have reasonable assessment of the physical quantities that play an important role in the light induced degradation of amorphous silicon solar cells.