Scientists from Stanford University have discovered how to make the electrical wiring on top of solar cells nearly invisible to incoming light. The new design, which uses silicon nanopillars to hide the wires, could dramatically boost solar-cell efficiency.
In most solar cells, the upper contact consists of a metal wire grid that carries electricity to or from the device. The wires, however, also act like a mirror and prevent sunlight from reaching the semiconductor, which is usually made of silicon.
The Stanford team placed a 16-nanometer-thick film of gold conducting metal on a flat sheet of silicon. The gold film was riddled with an array of nanosized square holes, but to the eye, the surface looked like a shiny, gold mirror.
To hide the reflective gold film, the engineers created nanosized silicon pillars that "tower" above the gold film and redirect the sunlight before it hits the metallic surface.
In addition to silicon, the new technology can be used with other semiconducting materials for a variety of applications, including photosensors, light-emitting diodes and displays and transparent batteries, as well as solar cells.