Modelling the light induced metastable effects in amorphous silicon

Abstract

We present results of computer simulations of the light induced degradation of amorphous silicon solar cells. It is now well established that when amorphous silicon is illuminated the density of dangling bond states increases. Dangling bond states produce amphoteric electronic mid‐gap states which act as efficient charge trapping and recombination centres. The increase in dangling bond states causes a decrease in the performance of amorphous silicon solar cells. To show this effect, a modelling approach has been developed which uses the density of localised states with exponentially increasing band‐tails and dangling bond defect states distribution chosen according to the defect pool model. The calculation of the evolution of dangling bond state density during illumination has been achieved through a dynamic scaling relation derived from a defect creation model. The approach considers the amphoteric nature of the dangling bond state and thus accounts for the contributions of the different charge states of the dangling bond during the degradation process. This paper attempts to describe the simulation approach which calculates the defect density as a function of energy, position in the solar cell and illumination time. In excellent agreement with other workers, our simulation results show that the increase in the density of neutral dangling bond states during illumination is higher than of the charged states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thin Film Silicon Solar Cells Under Moderate Concentration

“…In addition, we computed J-V characteristics using the one-dimensional model for semiconductor device simulation ASA, which is a product of the Delft University of Technology [5]. Simulations were performed with cell parameters approximating the measured cells and illuminations between 1 sun and 21 suns.…”

Optical properties of Se or S-doped hydrogenated amorphous silicon thin films with annealing temperature and dopant concentration

“…However, the problems of long-term stability and efficiency of this material have not been solved. The major cause of this instability is photoinduced degradation of a-Si:H thin films due to light-induced metastable Si dangling-bond defects [31][32][33][34][35][36]. It is documented that prolonged illumination of a-Si:H with bandgap light reduces photoconductivity [16].…”