Optimizing Folded Silicon Thin-Film Solar Cells on ZnO Honeycomb Electrodes

Abstract

A promising approach for low-cost nanostructured thin-film solar cells with enhanced absorption is the fabrication of zinc oxide (ZnO) honeycomb electrodes in a combined bottom-up process of nanosphere lithography and electrochemical deposition. To optimize the honeycomb structures, we investigate thin hydrogenated amorphous silicon (a-Si:H) solar cells (with 100 nm absorber thickness) on honeycomb electrodes with different periodicities in optical and electrical simulations; whereas the electrical performance is not significantly affected with changing periodicity, the short-circuit current density is reduced for increasing honeycomb diameter due to increased parasitic absorption of the electrochemically deposited ZnO. Furthermore, we demonstrate that for micromorph tandem solar cells with an intrinsic layer thickness of hydrogenated microcrystalline silicon (μc-Si:H) of >500 nm, a focusing effect occurs, which leads to a strong enhancement in the quantum efficiency in the microcrystalline bottom solar cell.