HEFOS – High Electric Fields at Organic Semiconductor Heterojunction Interfaces

• Applicant: Professor Dr. Sebastian Reineke, since 8/2021
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426730652

• Final Report Year: 2023

Final Report Abstract

HEFOS investigated the energy states of excited molecular states at type-II heterojunctions in organic semiconductor devices. The so-called charge-transfer states at such interfaces are of special interest for photovoltaic applications, photodetectors, as well as light-emitting diodes (LEDs). Heterojunctions are used in all these components to generate excited states (“excitons”) through light absorption or to generate light through exciton recombination. Such interfaces typically exhibit a significant voltage drop over a few nanometers, leading to high intrinsic electric fields. In contrast to intramolecular states, intermolecular charge transfer states sport an electric dipole extension of several nanometers. Therefore, their response to electric fields is significant. In LEDs and photodetectors, external voltages create external electric fields that superimpose these internal electric fields. The goal of this project was to manipulate the electric fields (both internal and external) at the interface of donor and acceptor materials to shift the spectral range of emission and absorption, i.e. to control the energy of the charge-transfer states. As a first result, we demonstrated that by using doped organic layers, it is possible to selectively manipulate the electric fields at the heterojunction to study the state energies. As a second result, we achieved the shifting of the energy states of charge transfer states at the interface through internal and external electric fields. This effect could be made visible to the naked eye through the change in emission color.

Publications

• Unraveling Structure and Device Operation of Organic Permeable Base Transistors. Advanced Electronic Materials, 6(7).
  Darbandy, Ghader; Dollinger, Felix; Formánek, Petr; Hübner, René; Resch, Stefan; Roemer, Christian; Fischer, Axel; Leo, Karl; Kloes, Alexander & Kleemann, Hans
  
• Electrical Pumping of Perovskite Diodes: Toward Stimulated Emission. Advanced Science, 8(17).
  Cho, Changsoon; Antrack, Tobias; Kroll, Martin; An, Qingzhi; Bärschneider, Toni R.; Fischer, Axel; Meister, Stefan; Vaynzof, Yana & Leo, Karl
  
• Electrothermal Tristability Causes Sudden Burn‐In Phenomena in Organic LEDs (Adv. Funct. Mater. 47/2021). Advanced Functional Materials, 31(47).
  Kirch, Anton; Fischer, Axel; Liero, Matthias; Fuhrmann, Jürgen; Glitzky, Annegret & Reineke, Sebastian
  
• Electrothermal Tristability Causes Sudden Burn‐In Phenomena in Organic LEDs. Advanced Functional Materials, 31(47).
  Kirch, Anton; Fischer, Axel; Liero, Matthias; Fuhrmann, Jürgen; Glitzky, Annegret & Reineke, Sebastian
  
• Enhancing sub-bandgap external quantum efficiency by photomultiplication for narrowband organic near-infrared photodetectors. Nature Communications, 12(1).
  Kublitski, Jonas; Fischer, Axel; Xing, Shen; Baisinger, Lukasz; Bittrich, Eva; Spoltore, Donato; Benduhn, Johannes; Vandewal, Koen & Leo, Karl
  
• Organic Permeable Base Transistors – Insights and Perspectives. Advanced Optical Materials, 9(14).
  Guo, Erjuan; Dollinger, Felix; Amaya, Baltasar; Fischer, Axel & Kleemann, Hans
  
• Reservoir computing with biocompatible organic electrochemical networks for brain-inspired biosignal classification. Science Advances, 7(34), eabh0693.
  Cucchi, Matteo; Gruener, Christopher; Petrauskas, Lautaro; Steiner, Peter; Tseng, Hsin; Fischer, Axel; Penkovsky, Bogdan; Matthus, Christian; Birkholz, Peter; Kleemann, Hans & Leo, Karl
  
• Reverse dark current in organic photodetectors and the major role of traps as source of noise. Nature Communications, 12(1).
  Kublitski, Jonas; Hofacker, Andreas; Boroujeni, Bahman K.; Benduhn, Johannes; Nikolis, Vasileios C.; Kaiser, Christina; Spoltore, Donato; Kleemann, Hans; Fischer, Axel; Ellinger, Frank; Vandewal, Koen & Leo, Karl
  
• Accurate Wavelength Tracking by Exciton Spin Mixing. Advanced Materials, 34(38).
  Kirch, Anton; Bärschneider, Toni; Achenbach, Tim; Fries, Felix; Gmelch, Max; Werberger, Robert; Guhrenz, Chris; Tomkevičienė, Aušra; Benduhn, Johannes; Eychmüller, Alexander; Leo, Karl & Reineke, Sebastian
  
• Interdot Lead Halide Excess Management in PbS Quantum Dot Solar Cells. Advanced Energy Materials, 12(45).
  Albaladejo‐Siguan, Miguel; Becker‐Koch, David; Baird, Elizabeth C.; Hofstetter, Yvonne J.; Carwithen, Ben P.; Kirch, Anton; Reineke, Sebastian; Bakulin, Artem A.; Paulus, Fabian & Vaynzof, Yana
  
• Simple Strategy to Measure the Contact Resistance between Metals and Doped Organic Films. Physical Review Applied, 18(3).
  Kirch, Anton; Fischer, Axel; Werberger, Robert; Aabi, Soflaa Shayan Miri; Maleckaite, Karolina; Imbrasas, Paulius; Benduhn, Johannes & Reineke, Sebastian
  
• Highly Crystalline Rubrene Light‐Emitting Diodes with Epitaxial Growth. Advanced Functional Materials, 33(14).
  Wang, Shu‐Jen; Kirch, Anton; Sawatzki, Michael; Achenbach, Tim; Kleemann, Hans; Reineke, Sebastian & Leo, Karl