The ’27plus6′ project aims for 33% efficient perovskite-silicon solar cell

The Institute for Solar Energy Research Hamelin (ISFH), the Karlsruhe Institute of Technology (KIT) and the Institute for Materials and Components in Electronics at the University of Hannover, as well as Centrotherm, Singulus, Meyer Burger and Von Ardenne, are involved in a research project aimed at achieving 33%-efficient perovskite-silicon tandem solar cell suitable for mass production.

The new research project is called '27plus6′ and it brings together the expertise of leading German and Swiss technology companies and research institutes. The consortium said that it aims to achieve the promised conversion efficiency under standard test conditions, and that is also seeking to reach a higher power yield, intended to accelerate industrial implementation.

The scientists explained that the real solar spectrum changes over the course of the day and varies seasonally and with geographical location. And for tandem cells, where the different layers may perform differently depending on the light conditions, adjusting the current for optimal output from both cells in a typical two-terminal configuration can be a difficult task.

Research projects have also investigated four-terminal setups as a way around this problem, but these appear to come with their own set of complications. The '27plus6' project will aim at developing 3-terminal cells, which it says are characterized by greater robustness in relation to changes to the solar spectrum. Combined with innovative new cell interconnection concepts, the consortium is convinced this approach will lead to higher energy yields from the cells.

The ISFH brings its expertise in the development of back-contacted silicon solar cells with passivating contacts to the project, and wants to further develop the deposition of perovskite absorbers on textured surfaces by means of co-evaporation. KIT, meanwhile, contributes its expertise in the field of perovskite cell development, for example, the realization of two-dimensional perovskite crystal structures.

The equipment suppliers will bring their considerable knowledge of mass production processes to the group. Centrotherm in particular states that it wants to further develop its processes for the deposition of passivating contact layers, and optimize these with a view to industrial-scale production.

According to the partners, with the demonstration of a significant increase in energy yield compared to today's silicon solar cells, the photovoltaic electricity production costs in Germany can fall below €0.04/kWh. Thanks to the high efficiency, special photovoltaic applications such as integration in electric vehicles are also conceivable.