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.
Naresh B. Kotadiya, Hao Lu, Anirban Mondal, Yutaka Ie, Denis Andrienko, Paul W. M. Blom & Gert-Jan A. H. Wetzelaer: Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies.
Nature Materials (2018)
About the Max Planck Institute for Polymer Research:
The Max Planck Institute for Polymer Research (MPI-P) ranks among the globally leading research centers in the field of polymer research since its foundation in 1984. The focus on soft materials and macromolecular materials has resulted in the worldwide unique position of the MPI-P and its research focus. Fundamental polymers research on both production and characterization as well as analysis of physical and chemical properties are conducted by scientific collaborators from all over the world. Presently over 500 people are working at the MPI-P, the vast majority of whom are engaged in scientific research.
Kerstin Felix | Max-Planck-Institut für Polymerforschung
Smart glass made better, and cheaper
08.03.2018 | University of Delaware
Lightweight hyperspectral imagers bring sophisticated imaging capability to drones
02.03.2018 | The Optical Society
At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.
Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...
The realisation of controllable large quantum devices is key for the development of quantum technologies.
Now a team of researchers from the University of Bristol, Peking University, Technical University of Denmark, ICFO Spain, PAS, University of Copenhagen and Dr....
The Fraunhofer Institute for Laser Technology ILT has developed an inline system for testing, qualifying and adjusting the focused powder jet of the nozzles of laser metal deposition machines. With this system, nozzles can be certified and the caustic characterized completely. The user can also visualize and monitor the process thanks to the camera module with integrated illumination.
Laser Material Deposition has already proven itself in various areas – for example when repairing tools or applying anti-corrosion coatings. But the result...
Scientists at the Max Planck Institute (MPI) for Polymer Research have developed the novel 2D TIRV spectroscopy technique to observe coupling between intramolecular and intermolecular vibrations that make water molecules “dance”.
Liquid water is permeated by a highly dynamic network of strong hydrogen bonds. Motions of molecules in this network underlie fundamental physical and chemical...
An Innsbruck team of experimental physicists, in collaboration with theorists from Innsbruck and Hannover, has for the first time observed so-called roton quasiparticles in a quantum gas. Empirically introduced by Landau to explain the bizarre properties of superfluid liquid Helium, these quasiparticles reflect an "energy softening" in the system as precursor of a crystallization instability. The new work published in Nature Physics demonstrate similar phenomena in the quantum-gas phase thanks to magnetic interactions, paving the way for a novel understanding of paradigmatic states of quantum fluids, such as supersolids.
Discovered in liquid helium about 80 years ago, superfluidity is a counterintuitive phenomenon, in which quantum physics and particle-wave duality manifest at...
08.03.2018 | Event News
06.03.2018 | Event News
05.03.2018 | Event News
12.03.2018 | Life Sciences
12.03.2018 | Medical Engineering
12.03.2018 | Power and Electrical Engineering