Showing papers by "Miro Zeman published in 2005"
08 Aug 2005
TL;DR: In this article, the defect density of solar cells with varying i-layer thickness is attributed to changes in defect density, which is linked to recombination processes in the material, and a good match between the experimental and simulated QE results is obtained.
Abstract: To use solar cells for space applications it is important to be able to predict the end-of-life (EOL) performance of the cell. To create a model to predict this EOL performance, quantitative information about degradation mechanisms is needed. In this paper we show quantum efficiency (QE) simulations and experimental results for high-energy electron beam irradiated solar cells. To study the depth dependence of the defect creation, solar cells with a varying i-layer thickness were irradiated. The changes in the QE are attributed to changes in the defect density of states of the material, which is linked to recombination processes in the material. Using this approach we are able to obtain a good match between the experimental and simulated QE results.
2 citations
TL;DR: In this article, the defect state distribution in a-Si:H was programmed by applying a particular bias voltage on the metal-oxide-semiconductor structure while annealing the structure above the equilibration temperature.
Abstract: The evolution of the programmed defect-state distributions in intrinsic hydrogenated amorphous silicon (a-Si:H) due to light soaking was qualitatively determined from charge deep-level transient spectroscopy. The defect-state distribution in a-Si:H was programmed by applying a particular bias voltage on the metal-oxide-semiconductor structure while annealing the structure above the equilibration temperature. The programmed distributions simulate defect-state distributions in different parts of an actual a-Si:H solar cell, particularly in the intrinsic regions close to thep/i and i/n interfaces. The defect-state distribution in the bulk of the intrinsic layer is characterized by comparable contributions from the positively charged defect states above midgap, Dh, neutral states, Dz, and negatively charged states below midgap, De. In the programmedp-type (n-type) defect-state distribution there is an excess of the Dh (De) states. Light exposure modifies the p-type distribution that evolves to a broad distribution of states with a maximum around midgap. This distribution is dominated by Dz states with substantial contributions from Dh and De states. In case of n-type distribution light soaking only slightly influences the distribution by removing a part of the Dh states and by a small increase of Dz and De states.
1 citations