AIXTRON SE

Decisive progress in multi-junction solar cells / Record efficiency of highly efficient III-V multi-junction solar cells on silicon / High energy efficiency at attractive cost - Seite 2

Low price - High cost attractiveness of silicon wafers

In this so-called tandem photovoltaics, different combinations of high-performance solar cell materials are arranged in layers on top of each other in order to use the different wavelengths of sunlight more efficiently when converting light into electrical energy. Silicon is suitable for absorbing the infrared portion of the sunlight spectrum. Layers of different III-V semiconductor compounds, a few micrometers thick, are then applied to the silicon base to convert the ultraviolet, visible and near-infrared light more efficiently into electricity. Tandem photovoltaics is a key technology for the energy transition. Due to the silicon used, the multi-junction solar cells grown on a silicon substrate are more cost-effective than solar cells based on other substrates.

Work on faster crystal growth to further reduce manufacturing costs

From the technological basis that has now been achieved, the alliance partners are working at high pressure to further increase efficiency and reduce manufacturing costs. To this end, the deposition of the layers is to be realized even faster, with higher throughput and thus more cost-optimized. In addition, the efficiency of the solar cells is to be further improved.

"Specifically, the dislocation density in the III-V solar cell layers is to be reduced from 108 cm-2 to the range of 1-5*106 cm-2 in order to increase the efficiencies to more than 30 percent. And last but not least, the cost-effectiveness of the epitaxy processes is to be further optimized," explains Prof. Dr. Michael Heuken, Vice President Corporate Research and Development at AIXTRON SE.

By means of more cost-effective processes in combination with silicon as the lowest sub-cell, tandem technology is to be made accessible for broad-based photovoltaics in the future. AIXTRON has already been working on such III-V multi-junction solar cells on silicon with several partners for many years.

The project "SiTaSol" for the joint development of layer packages that can be produced as quickly and cheaply as possible is funded by the EU. In "SiTaSol" AIXTRON has built and tested a specially optimized Metal Organic Chemical Vapor Phase Epitaxy (MOVPE) system in its own laboratory.