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Institute of Energy and Climate Research

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Research Group Materials and Solar Cell Development

We develop and investigate materials for application in thin film solar cells. The focus is on alloys on the basis of amorphous and microcrystalline silicon, i.e. a-Si:H and µc-Si:H such as a/µc-SiGe:H, a/µc-SiO:H und a/µc-SiC:H, all so-called “disordered semiconductors”.
The materials are prepared with methods where gaseous precursors are decomposed or synthesized in a controlled manner, which then deposit at a comparatively low substrate temperature of 200°C on glass- metal- or plastic substrates. Preparation methods like Plasma-Enhanced Chemical Vapour Deposition or Hot-Wire Chemical Vapour Deposition are optimized in view of the desired material properties and in view of possible technical applications and up-scaling to industrial processes (s. process technology group).
A characteristic property of such materials is their structural disorder which distinguishes them from crystalline semiconductors. This disorder leads to structural defects which strongly influence the optical and electronic properties of the materials and therewith their possible application in solar cells. The defects are investigated with methods like e.g. electron spin resonance or photoconductivity spectroscopy, trying to understand the relationships between disorder and defects with preparation methods on the one hand and with opto-electronic properties on the other hand.
Finally the materials are applied in thin film solar cells. Rigid (glass, metal) as well as flexible (metal, plastic) substrates are used. Besides single junction solar cells, in particular multi junction stacked solar cells are developed which are better matched to the solar spectrum and which yield higher efficiencies. The complex layer stacks with layers as thin as a few nanometers only, require an optimization and control of all individual process steps. As pre-requisite for this, the depositions systems at the institute have been developed on the highest technical and scientific standard in close cooperation with industry partners.

ZellübergangSchemazeichnung des Übergangs von Dünnschicht-Silizium mit mikrokristalliner (links) zu amorpher Mikrostruktur (rechts)