Experimental Demonstration of Light-Trapping Transparent Electrode Geometries

The intrinsic trade-off between conductivity and transparency has long impeded the development of truly transparent electrodes. Recently, a transparent electrode design was introduced that promised remarkably high electrical conductivity while allowing near-complete transmission of incident light into the underlying optical device. The approach is based on the use of metallic wires with inclined surfaces, embedded in a transparent dielectric film. Light reflected by metallic regions of the sample can be recovered by total internal reflection, resulting in efficient trapping of light incident on conductive regions. Prototype electrode geometries were fabricated by multiphoton lithography and selective chemical deposition. Light trapping is observed by optical microscopy and laser scanning experiments for surface tilt angles exceeding 25 degrees. Approximately 60% of light reflected by the metallic electrode surface was recovered through total internal reflection. The presented approach could lead to optoelectronic devices with significantly improved performance across a wide spectral bandwidth.