Assessing the Potential of Inversion Layer Solar Cells Based on Highly Charged Dielectric Nanolayers

The production and performance of p-type inversion layer (IL) Si solar cells, manufactured with an ion-injection technique that produces a highly charged dielectric nanolayer, are investigated. It is demonstrated that the field-induced electron layer underneath the dielectric can reach a dark sheet resistance of 0.95 kΩ sq⁻¹ on a 1 Ω cm n-type substrate, lower than any previously reported. In addition, it is shown that the implied open-circuit voltage of a p-type IL cell precursor with a highly charged dielectric is equivalent to that of a cell with a phosphorous emitter. In the cell precursor, light-beam-induced current measurements are performed, and the uniformity and performance of the IL is demonstrated. Finally, simulations are used to explain the physical characteristics of the interface leading to extremely low sheet resistances, and to assess the efficiency potential of IL cells. IL cells are predicted to reach an efficiency of 24.5%, and 24.8% on 5/10 Ω cm substrates, by replacing the phosphorous emitter with a simpler manufacturing process. This requires a charge density of beyond 2 × 10¹³ cm⁻², as is demonstrated here. Moreover, IL cells perform even better at higher charge densities and when negative charge is optimized at the rear dielectric.