Ultralow Optical and Electrical Losses via Metal-Assisted Chemical Etching of Antireflective Nanograss in Conductive Mesh Electrodes

Various types of anti-reflective technologies are capable of increasing the light absorption of optical devices. The electrical conductivity of the collected carriers must also be increased for efficient photoelectric conversion. However, increasing the front electrode area reduces the amount of light absorption, causing shading and resistive losses to conflict in front-illuminated devices. In this study, a low-reflectance surface and high-conductance electrode for Schottky photodiodes are fabricated using metal-assisted chemical etching (MacEtch). Si nanograss (SiNG) and Ag-mesh formed via MacEtch serve as a subwavelength surface and buried electrodes, respectively. SiNG increases light absorption without causing shading loss, while the buried Ag-mesh considerably improves electrical conductivity. The SiNG/Ag-mesh structure exhibits a solar weighted reflectance of 1.20% and a sheet resistance of 5.48 Ω □⁻¹. The SiNG/Ag-mesh Schottky photodiode exhibits an external quantum efficiency of 89.5% at a wavelength of 860 nm and an internal photoemission effect in the sub-band gap. The self-organized SiNG/Ag-mesh, fabricated through a simple wet-etching method, simultaneously addresses the issues of optical and electrical losses, enabling the application of this technique to a wide range of optoelectronic devices.