Investigation into efficiency-limiting defects in mc-Si solar cells

O. A. Al-Ani, A. M. A. Sabaawi, J. P. Goss, N. E. B. Cowern, P. R. Briddon and M. J. Rayson
Solid State Phenomena

First-principles quantum-chemical simulations are combined with TCAD device modelling to examine the impact of the intrinsic stacking faults and &Sigma5-(001) twist grain-boundaries on the performance of solar cell efficiency. We find from the combination of these computational methods, the optical properties of ideal stacking faults are similar to those of pure Si, whereas the optimised grainboundary leads to a clear change in the real and imaginary parts of refractive index, increasing the solar-cell current density, and thus the solar cell efficiency. The impact at a device level is dependent upon the areal density of such material. So far as the optically absorption and carrier generation is concerned, segregation of diffusing iron at these planar defects has a negligible impact on device characteristics, but non-radiative recombination processes and carrier traps due to iron are expected to significantly affect efficiency in these regions.

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