Physicists at the HZDR and TU Dresden have developed a photodetector made entirely of layers of metal-organic frameworks. As the compound can detect a broad wavelength range of light and convert it into electrical signals and is also inexpensive, it could be used as a new type of detector material for digital cameras and many other electronic applications.
Metal-organic frameworks (MOFs) are highly porous materials that consist of up to 90 percent empty space. The metal-organic framework compound developed at TU Dresden consists of an organic material with incorporated iron ions. What is special about it is that the scaffold forms superimposed layers with semiconducting properties, which makes it interesting for potential applications in optoelectronics. At 400 to 1575 nanometers, the semiconductor can detect a wide range of wavelengths of light, ranging from ultraviolet radiation to the near infrared. The spectrum of wavelengths that a semiconductor material can detect and convert into electrical signals essentially depends on the band gap. The smaller the band gap, the less energy is required to excite an electron. Because this is very small for the material under investigation, even a small amount of light energy is sufficient to induce a current. The performance can be further improved by cooling the detector to lower temperatures, as this suppresses the thermal excitation of electrons. Further improvements are possible by optimizing the component configuration, producing reliable contacts and further developing the material. The next step is to significantly reduce the layer thickness. The aim is to reduce the stacked layers to 70 nanometers if possible. Up to this layer thickness, the material should still have comparable properties. If it can be proven that the functionality is retained in a significantly thinner layer, further development can begin until the material is ready for production.
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), www.hzdr.de
