Lateral solar cells promise bright future

A team of US engineers have created high performance, micro-scale solar cells that could power a wide range of personal devices.

Lateral solar cells are a form of solar cells which are able to convert more incoming light into energy than ‘traditional’ solar panels. These miniature solar cells could be used to power personal devices such as smartwatches, autofocusing contact lenses and wearable medical sensors.

Professor Hongrui Jiang, from the University of Wisconsin-Madison and author of the study published in Advanced Materials Technologies, said: “From a fabrication point of view, it is always going to be easier to make side-by-side structures. Top-down structures need to be made in multiple steps and then aligned, which is very challenging at small scales.”

The traditional top down arrangement means photovoltaic cells are made of two electrodes surrounding a semi conducting material. When light hits the first electrode, charge travels through to the bottom layer, creating an electric current.  Jiang’s group instead created a densely packed side to side version, in effect rotating the solar cells 90°. This allows the light harvesting and charge conducting features of the solar cell to be solely the responsibility of separate components — unlike in top down solar cells.

Existing lateral new-generation solar cells convert almost two percent of incoming light into electricity. The researchers’ cells were able to convert almost three times as much, possibly due to so many electrodes being present in such a small volume.

Jiang said: “In other structures, a lot of volume goes wasted because there are no electrodes or the electrodes are mismatched. The technology we developed allows us to make very compact lateral structures that take advantage of the full volume.”

The research team will now work on making their solar cells even smaller and efficient by finding materials that can increase transparency and conductivity.