The aim of photon management is to increase solar cell efficiencies by either splitting or modifying the spectrum of sunlight before it hits the solar cell, or by altering the light’s path inside the solar cell in such a way that more light is absorbed. This increases efficiency and lowers the cost per kWh for the electrical energy produced. A major advantage of this technology is that it can be combined both with existing technologies like crystalline silicon, and with emerging technologies like organic solar cells.
One particular area of focus is the use of advanced optical concepts to improve light absorption in solar cells. These include nano- and microstructures that provide the solar cell surface with antireflection properties and thereby ensure that more light reaches the solar cell. By using photonic structures on the front of the cell that selectively reflect light depending on its angle and energy, and by using diffractive or other structures that redirect light on the rear, light can be prevented from exiting the solar cell.
The majority of solar cells available today consist of a single semiconductor material with a p-n junction. Such cells are only able to utilize part of the energy in the solar spectrum. In the business area of Photon Management, we develop concepts and technologies that can be employed to overcome such basic limitations in conventional solar cell efficiency. Upconversion is a key aspect of our research in this field. Some 20% of the photons contained in sunlight possess too little energy to be used by silicon solar cells. Upconversion generates one high energy photon that can then be utilized by the solar cell out of two or more low energy photons.
Our work encompasses the development of new concepts, developing and characterizing materials, and manufacturing complete solar cell systems with new functionalities.