Research and Development Platform HEMF

HEMF research projects at the Forschungszentrum Jülich

Within the the Forschungszentrum Jülich three subprojects exist in the framework of HEMF dealing with the topics

• Semiconductors for Photovoltaic (T1)
• Solar fuels (S1 and M1)
• Fuel cells (S1 and M1)

Please contact the responsible instrument officer for detailed information about the definite start of user operation.

Semiconductors for Photovoltaic

Subproject T1
Deposition tool, co-evaporation & glovebox for perovskite solar cells and tandem cells

The general purpose of the equipment is to make different variants of perovskite solar cells, including perovskite-crystalline Si tandem cells, perovskite-perovskite tandem cells and perovskite single junction solar cells. The equipment consists essentially of two parts, a deposition cluster and a co-evaporation chamber that is attached to a glovebox. The deposition tool allows the fabrication of passivation layers, contact layers and tunnel junctions based on amorphous and microcrystalline silicon based alloys for tandem solar cells. The co-evaporation chamber allows the fabrication of the perovskite absorbers and the glovebox allows users to combine the vacuum processes with wet-chemical processes, to encapsulate the device and to anneal layers in nitrogen atmosphere.

Perovskite solar cells are promising for various reasons. They have relatively high efficiencies despite the fact that they can be made quite easily using wet chemical methods or co-evaporation. This is even more remarkable because it is one of the few high band gap materials with high efficiencies > 17 %. Therefore, using perovskite based absorbers in two terminal tandem devices will be a strategy to make the most out of the potential of perovskites. The facilities in Jülich allow making such solar cells and allow the users to choose from a variety of different deposition techniques to make contact layers, tunnel junctions and transparent conductive oxides. In addition, co-evaporation allows better conformal deposition on rough or nanostructured surfaces that is used to increase absorption by scattering of light at interfaces. We study in detail the optical properties of the layers and try to optimize light trapping in single and multi-junction solar cells.

Benefits for external users

• External users can bring in part of the tandem stack prepared, developed and optimized in their home institution and prepare the rest in the HEMF facility to test the complete stack
• Device, materials and interface characterization is available in Jülich and external users can benefit from that
• In particular solar cell characterization optimized for tandem cells is available for HEMF users                                                                                                     
  

Solar Fuels and Fuel Cells

Subproject S1
Processing system with in-situ monitoring for nanocrystalline perovskites

Nanocrystalline perovskite materials are key components in batteries and fuel cells with respect to their catalytic function in electrodes and with respect to their transport properties for solid state electrolytes. The processing of nanocrystalline oxide materials is highly challenging and requires a complete process chain including in-situ process control.

Subproject M1
Aliovalently-doped perovskite ceramics for electrodes and electrolytes

Reducing the operating temperature of SOFCs and SOECs below 600°C is one of major goals of the POF-III program. A promising route is the development of proton-conducting oxide materials with perovskite structure. Aliovalent doping with transition metals will further enable us to tailor the physical properties and ion conductivity of these materials.

Nuclear magnetic resonance (NMR) is ideally suited to probe the mobility over a wide range of rate constants and length scales. Furthermore, the electrochemical stability and degradation of electrode as well as electrolyte materials can be probed. Electron paramagnetic resonance (EPR) is complementary to NMR as it probes the existence of paramagnetic centers with a non-vanishing electron spin. It allows the quantification of the oxidation state of aliovalent dopants and its temporal change. The neighborhood of an electron spin can be investigated using electron–nuclear double resonance (ENDOR) experiments.

The backbone of this lab is a high-field NMR spectrometer and a pulsed EPR instrument. The NMR spectrometer is equipped with a 17.5 T widebore NMR magnet and with gradient amplifiers for imaging and diffusometry. The EPR spectrometer operates at the X and the Q frequency bands, and is equipped for ENDOR experiments. For the characterization of materials, commercially available probes are used whenever possible.