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The Midgap State Influence on Space Charge Density of aSi:H p-i-n i-layer

The nature and distribution of midgap states in a‐ Si:H p‐i‐n solar cell has been investigated using the response measurements on voltage and light pulses out of phase. The experimental results were analyzed using numerical model based on the S. R. Dhariwal and S. Rajvanshi’s theory. The energy distributions of midgap states were obtained from fitting the measured responses on simultaneous light and voltage pulses to exponential curves. Further, the space charge density and recombination rate are numerically simulated. It is found that the midgap densities of states, which are exited with voltage and light pulses, are located in vicinity of the p‐i junction. The responses shape changes with the increasing voltage magnitude at given light intensity. For a small voltage magnitudes, less than critical voltage, space charge density decrease in vicinity of p‐i junction. For voltages up to threshold voltage of specific response shape, the small changes in width of space charge region occurs. In time after light and voltage excitation, the main changes in space charge density occur in p‐i region. Increase of light wavelength increases the space charge density in p‐i region and enlarges the neutral region versus n‐i junction. Proposed method can be used for dangling bond midgap states characterization.

midgap state; space charge density; recombination rate; a-Si:H; transient response; solar cells

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