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Institute of Energy and Climate Research

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Photovoltaic-electrochemical devices

The group is working on development of low cost thin-film silicon multi-junction layer stack solar cells and their integration in solar modules. The focus of the Device development group is on tandem and triple-junction solar cells containing hydrogenated amorphous (a-Si:H) and microcrystalline (µc-Si:H) silicon with optimized power conversion adapted to the entire solar spectrum. The triple-junction devices concept provides high conversion efficiency and wide-range tunable output voltages (1-3 V). The possibility to vary the output voltage of thin-film silicon technology is unique. It can be used for future applications in combination with other technologies like electrochemical energy storage in a coupled battery or hydrogen production via photoelectrochemical water splitting.
One objective of our work is to improve the light management and overall cell efficiency of multi-junction devices by replacing the conventional doped layers with novel highly transparent and conductive layers made of hydrogenated silicon oxide alloys (a/µc-SiOx:H). Our goal is the successful implementation of µc-SiOx:H layers as window layer, intermediate and back reflector layers in multi-junction solar cells.
Preparation method like Plasma-Enhanced Chemical Vapour Deposition (PECVD) is used to deposit and to study different types of multi-junction silicon solar cells and silicon oxygen alloy materials. The PECVD process is optimized in view of the desired material properties and in view of possible technical applications and up-scaling to industrial processes.

Another field of work of the group is the analysis of influences of impurities (oxygen and nitrogen) on the material properties of a-Si:H and μc-Si:H films and on the corresponding solar cell performances. For the fabrication of a-Si:H and μc-Si:H p-i-n solar cells with high efficiency a low concentration of impurities in the i-layer are required. The outstanding achievement of the group is the finding that a high amount of oxygen than was previously assumed can be incorporated in thin-film silicon without deteriorating the device quality using new deposition regimes. Thus lower-cost PECVD equipment and lower-cost processes can be applied and a significant cost reduction can get achieved.


Research Facilities, Experimental Setups and Methods



Dr. Tsvetelina Merdzhanova
Phone: +49 2461 61-3177