Photovoltage Management Based on Enhanced Excitation Levels in Surface Arrays of Subwavelength Silicon Formations

Surface arrangements of subwavelength formations are extensively discussed in the context of photocurrent enhancement for photovoltaic (PV) applications. Recently, the potential contribution of such arrangements toward photovoltage augmentation is suggested. This study numerically demonstrates the potential for photovoltage management based on arrays composed of inverted silicon cones, referred to as light funnel (LF) arrays. The transition from an optimized nanopillar (NP) array into an LF array is examined. It is shown that a decrease in NP bottom diameter (D_b) is accompanied by an increase in open-circuit voltage (V_oc). The highest photovoltage enhancement is recorded for the smallest considered D_b = 50 nm with a V_oc increase of 75 mV and reflects a 22% V_oc enhancement compared with the NP V_oc. It is shown that this V_oc increase is due to 250% increase in the excitation level, and that the spatially resolved excitation level of the array-nested LFs is more than two orders of magnitude higher than the highest spatially resolved excitation level in the array-nested NPs. Finally, it is shown that the suggested photovoltage management entails almost a factor of 2 increase in the nominal power conversion efficiency upon the transition from an NP PV cell into LF PV cell.