| Summary: | 碩士 === 國立中興大學 === 光電工程研究所 === 105 === To understand the effect of oxygen contamination on the electronic and optical properties of a-Si:H, computer simulation has been used. AFORS-HET (Automata for Simulation of Heterostructures) has been used to simulate a-Si:H p-i-n solar cells, which have i-layers, contaminated by oxygen. The contamination of i-layer effects the photovoltaic process in the solar cell, leading to inefficient collection of carriers in the bulk of the i-layer.
The changes in the electronic structure of a-Si:H due to oxygen contamination have been gathered from literature. It was found that the Gaussian defects in the i-layer are mainly affected by oxygen contamination. The peak defect density increases with oxygen contamination. The Gaussian defects shift closer to the valence band, EV, because of increase in n-type nature. The exact value of peak defect density has been evaluated through numerous simulations, by increasing the peak defect density, until the simulated solar cell’s fill factor becomes closer to the experimental values. These evaluated values have been used to model two solar cells, which have already been experimentally developed. These solar cells have different levels of oxygen contamination. The simulated I-V, QE and QE values closely match the experimental values, and hence, verify the correctness of the physical model for oxygen.
Next, two other solar cells have been simulated. These solar cells have i-layers which have been deposited under different deposition conditions. Hence, the i-layers have different band-gap, thickness and oxygen contamination. These solar cells have been simulated, and the oxygen model, previously developed, has been employed in these two simulations. The simulated results closely match the experimental results, and hence provide additional verification to the proposed model for oxygen contamination.
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