15-Mar-2018 - Max-Planck-Institut für Polymerforschung

OLED: Nanometer-thin layer improves efficiency

Scientists at the Max Planck Institute for Polymer Research in Mainz, Germany, have received an unexpected result: They have discovered a new method to improve contacts in OLEDs. This new approach leads to a higher energy efficiency and can be used in almost any organic semiconductor element.

Organic light-emitting diodes (OLEDs) are used as light sources in high-quality smartphone displays and large-area high-end products such as OLED televisions. The main active component in an OLED is a light-emitting layer of an organic semiconductor, which converts electrical energy into visible light. In an OLED, the organic semiconducting layer is situated between two electrodes; by applying a voltage across these two electrodes, an electric current passes through the OLED, which is converted into visible light.

However, for many organic semiconductors, especially for blue- or ultraviolet-emitting materials, it is difficult to inject the current from the positive electrode into the OLED. This leads to low efficiencies in OLEDs.

Dr. Gert-Jan Wetzelaer, Group Leader at the Max Planck Institute for Polymer Research in Mainz, Germany, has recently discovered a way of improving the current injection from the positive electrode in OLEDs. Wetzelaer and his team have covered the positive electrode with an ultrathin layer of another organic semiconductor as a spacer layer between the electrode and the light-emitting organic semiconductor. Wetzelaer said: “The result was unexpected. This nanometer-thin layer facilitates charge transfer between the electrode and the organic semiconductor. Although it seems to be illogical at first, eliminating physical contact between electrode and semiconductor actually improves the electrical contact.”

Improved contacts in semiconductors

Improving electrical contact with an ultrathin interlayer greatly increases the efficiency of ultraviolet-emitting OLEDs. The scientists at the MPI for Polymer Research have demonstrated this improvement of electrodes for a large number of organic semiconductors and for different spacer layers. Professor Paul Blom, Director at the Max Planck Institute for Polymer Research and head of its Molecular Electronics Department, is convinced: “This simple method of covering electrodes in OLEDs with an ultrathin layer for current-injection improvement is a resounding success for technical application in high-end electronics.”

Gert-Jan Wetzelaer and his research team are very confident that this new approach for fabricating improved contacts can be used in basically any organic-semiconductor device, which could boost their performance now.

Facts, background information, dossiers
More about MPI für Polymerforschung
  • News

    Microscopic structures could further improve perovskite solar cells

    Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber fro ... more

    When ions rattle their cage

    Electrolytes play a key role in many areas: They are crucial for the storage of energy in our body as well as in batteries. In order to release energy, ions - charged atoms - must move in a liquid such as water. Until now the precise mechanism by which they move through the atoms and molecu ... more

    Harnessing the rain for hydrovoltaics

    Drops of water falling on or sliding over surfaces may leave behind traces of electrical charge, causing the drops to charge themselves. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz have now begun a detailed investigation into this phenomenon that accompanies ... more

More about Max-Planck-Gesellschaft
  • News

    COVID-19 impacts on the Earth System

    COVID-19 immediately affects the health, economy and social well-being in our personal lives. Yet, the consequences on the entire Earth System, in particular the ones emerging from the widespread sheltering and lock-down measures, may be much more far-fetching and long-lasting. This has bee ... more

    Self-healing soft material outsmarts nature

    A soft material that heals itself instantaneously is now reality. A team of scientists at the Max Planck Institute for Intelligent Systems and at Pennsylvania State University tune the nanostructure of a new stretchable material in such a way that it now entirely recovers its structure and ... more

    Microscopic structures could further improve perovskite solar cells

    Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber fro ... more