There are two primary ways to increase the energy output of a solar cell. You can improve the conversion efficiency, so more of the light that is absorbed is converted to electricity, and you can increase the range of light the cell can absorb. The latter is very difficult though as it is limited by what materials you are using, but research from Fraunhofer-Gesellschaft may help with that.
Silicon, which is a common material for many commercial solar cells, is not able to absorb infrared light, which makes up a decent amount of sunlight. Black silicon though does absorb infrared light, but is not greatly efficient. The researchers changed that by improving the production method. Black silicon is made by shining a femtosecond laser onto a piece of silicon in a sulfur-containing atmosphere. The sulfur binds to the silicon and acts like a catalyst, enabling electrons excited by infrared light to enter the conduction band. This effect works in both directions though, so electrons had an easier time going up and falling down. By changing the shape of the laser though, the researchers were able to create a bias, so the electrons were less-able to fall.
The researchers hope to see black silicon eventually integrated into traditional silicon solar cells, where the black silicon is behind the regular silicon, and catches what infrared light comes through. To help achieve this, the researchers are looking to form a spin-off company to market their laser system to manufacturers.