Solar cells are generally flat, but by adding minuscule silicon pillars to the surface, researchers at the University of Twente research institute MESA+ in the Netherlands have been able to more than double the amount of energy produced. In an article published in Advanced Energy Materials, they now report the optimum height and doping depth for these pillars.

Last year, the University of Twente researchers succeeded in creating a semiconductor fitted with one million minuscule pillars per square centimeter, with these pillars able to convert sunlight into electricity. The semiconductor is made of two types of silicon: one is ‘contaminated’ with boron and the other with phosphorus. The transition between both types of silicon, known as the PN junction, is essential for the efficiency of the solar cell, as the positive and negative charges are separated at this junction. The challenge in creating the pillars was to make sure that the PN junction followed the structure of the surface as accurately as possible.

In this new study, the same researchers tried to discover the pillar height and PN junction depth at which the semiconductor works most efficiently. The answer they came up with was 40μm high and 790nm deep, at which 13% of the sunlight falling on the surface is converted into electricity. This represents more than double the efficiency of a flat structure, where no more than 6% of the sunlight can be converted into electricity.

This research forms part of a large-scale project in which various research groups at the University of Twente are working together on a ‘solar-to-fuel’ device that can convert sunlight directly into a fuel such as hydrogen gas. The pillars have two functions when used for this purpose – not only do they increase the amount of sunlight that can be captured, but they also enlarge the reaction surface area on which hydrogen can be produced.

The pillars can also obviously be used to make solar cells more efficient. However, senior author Jurriaan Huskens does not expect the pillars to be particularly worthwhile for regular solar panels because of the higher costs of production. Nonetheless, the technology could prove useful for specific technologies.

This story is adapted from material from the University of Twente, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.