Abstract
We investigate the accuracy of rigorous coupled-wave analysis (RCWA) for near-field computations within cylindrical GaAs nanowire solar cells and discover excellent accuracy with low computational cost at long incident wavelengths but poor accuracy at short incident wavelengths. These near fields give the carrier generation rate, and their accurate determination is essential for device modeling. We implement two techniques for increasing the accuracy of the near fields generated by RCWA and give some guidance on parameters required for convergence along with an estimate of their associated computation times. The first improvement removes Gibbs phenomenon artifacts from the RCWA fields, and the second uses the extremely well-converged far-field absorption to rescale the local fields. These improvements allow a computational speedup between 30 and 1000 times for spectrally integrated calculations, depending on the density of the near fields desired. Some spectrally resolved quantities, especially at short wavelengths, remain expensive, but RCWA is still an excellent method for performing those calculations. These improvements open up the possibility of using RCWA for low-cost optical modeling in a full optoelectronic device model of nanowire solar cells.
Highlights
Nanowire solar cells (NWSC) are a new solar cell technology with the potential to improve upon existing solar cell devices
We show that rigorous coupled-wave analysis (RCWA) can be used for accurate optical modeling of nanowire solar cells
The first is an implementation of an existing technique, which we call the continuous variable formulation (CVF), which mitigates the Gibbs phenomenon and ensures proper discontinuities at interfaces by modifying the field computations such that only quantities that are continuous in real space are reconstructed from their Fourier components [15]
Summary
Nanowire solar cells (NWSC) are a new solar cell technology with the potential to improve upon existing solar cell devices. The normal components of E should be discontinuous across material boundaries, but a Fourier reconstruction requires an intractable number of terms to accurately model such a discontinuity, even though far-field quantities such as the total absorptance may be well converged. The first is an implementation of an existing technique, which we call the continuous variable formulation (CVF), which mitigates the Gibbs phenomenon and ensures proper discontinuities at interfaces by modifying the field computations such that only quantities that are continuous in real space are reconstructed from their Fourier components [15]. The second technique uses the well-converged, highly accurate far-field computation of each layer’s absorption to rescale the near fields, ensuring correct total generation within a device layer
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