Computer analysis of induced-inversion layer MOS solar cells

Abstract

A computer analysis of induced inversion layer MOS solar cells is described. The analysis simultaneously solves Poisson's equation and the continuity equation in one dimension and provides a very effective method for solar cell evaluation. Numerical solutions of the carrier continuity equation in the inversion layer illustrate how cell designs may be improved in order to obtain higher short wavelength spectral response. Very shallow junctions (on the order of 0.07-0.1 μm) are shown to be optimum with higher electric fields in a direction to aid the collection of carriers generated by very high energy photons. The results also indicate that induceed inversion layer cells are less sensitive to surface recombination velocity variations than diffused p- n junction cells and have higher minority carrier lifetime. Furthermore, the effect of a p- p + low-high junction on the back surface is examined and the results indicate that it is insignificant when the substrate doping concentration is optimized. High inversion layer sheet resistance values are evaluated and minimized with the contact diffusion used in the analysis designed to reduce the high inversion layer sheet resistance. Design improvements in cell performance are evaluated and identified with further improvement possible here. Conversion efficiency for silicon of 17.3% at AMO in the inversion layer solar cell is predicted assuming 95% transmission through the transparent conductor.