In search of the perfect silicon solar cell

Dr. Mathias Müller examining a solar cell.
Highly efficient silicon solar cells with zero degradation: In a current project named ZORRO researchers of the Institute of Applied Physics are devel-oping such cells. Together with partners they will be optimizing the solar efficiency and the energy yield per module of modern solar cells.

While renewable resources are part of today’s energy mix the use of sunlight in PV solar modules has a leading role. Crystalline silicon technologies are mostly used with a 95% share of the PV world market. The development of the so called PERC solar cell (Passivated Emitter and Rear Contact) has been elevating the degree of efficiency perceivably. Efficiency is currently at over 22 % for monocrystalline and for about 20 % for basic multicrystalline silicon material. However, PERC solar cells tend to degrade while in use. This means that the degree of efficiency of the solar cell might be losing several percentage points. One of the reasons for degradation is the lighting at high temperatures, the so called LeTID-phenomenon (Light and elevated Temperature Induced Degradation). Even if this phenomenon can be eliminated in some cases, researchers still have not fully examined its mechanisms and causes on a material basis.

A new concept for zero degradation in the industrial production of multi- and monocrystalline PERC solar modules is therefore in the focus of the joint research project ZORRO. To conduct fundamental research the scientists will use the modern clean room laboratory at the Institute of Applied Physics at TU Bergakademie Freiberg. There, the researchers will analyse the causes for degradation and simulate the effects on solar efficiency and energy yield per module. The main focus is on the interdependences between impure elements in the wafer material and oxygen, which is being inserted during the production of the solar cell.

The projects consortium consists of four research institutions as well as two associated industrial partners. The project coordinator Fraunhofer IISB in Erlangen is responsible for the production of deliberately contaminated silicon material. The International Solar Energy Research Center Konstanz e.V. will produce the PERC solar cells. The examinations of defect and degradation will be conducted at University of Konstanz and the Institute of Applied Physics at U Bergakademie Freiberg. Wacker Chemie AG and Centrotherm International are associated industrial partners. The project is funded by the Federal Ministry for Economic Affairs and Energy.

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Dr. Mathias Müller, Tel.: 03731-39-2162