Silicon solar cells are the backbone of the photovoltaic industry with a rich history. Cell efficiencies up to 26.7% have been reached, close to the fundamental Auger limit for this material. But the industrial deployment came with the requirement of reaching extremely low manufacturing costs which influenced the most successful cell structures on the market. But efficiency stays a key objective of research and industrial deployment. This lecture class embarks deeply into the field from history to present challenges and future ideas.

Speakers / Authors:
Dr. Pierre Verlinden/Amrock
Prof. Stefan Glunz/ Fraunhofer ISE

The Crystalline Silicon PV technology has a very long history, from the first silicon cells (a few percent efficient) at Bell Labs in 1954, to a current world record of 26.7% for a single junction silicon solar cell. The evolution of silicon cell design, from a simple p-n junction to a more sophisticated solar cell with passivated front and rear surfaces and passivating contacts, already well predicted in the 1970’s to 1990’s, have taken years of R&D and industrial experiments to bring more efficient cell designs to cost-effective commercialization. Thanks to multiple innovations and step improvements brought by cost-conscientious industrialization, efficiencies of solar cells in large volume production have reached levels >23%, unexpected, even ten years ago.

The tutorial will also show how Auger recombination is limiting the single-junction silicon cell efficiency to about 29.4% and how we can approach this efficiency limit in practical solar cells with existing or future cell designs. The possible future improvements in efficiency with n-type or p-type devices, with front or rear junction, will be studied. Such optimized silicon solar cells are ideally suited as bottom cells for tandem solar cells, allowing to go beyond the 29.4% efficiency limit.

We will also review the challenges to ramp up the annual production to several TW per year. The PV industry is now facing an additional challenge. After focusing mainly on efficiency, cost and reliability, the industry must make sure that the technologies in line for multi-Terawatt of annual production are sustainable in terms of materials used in their fabrication and the recycling of the finish products.