Polymeric Emitters with Controllable Thermally Activated Delayed Fluorescence for Solution-processable OLEDs (2019–2021)

Principal investigators from three sides:

Latvia Martins Rutkis Institute of Solid State Physics, University of Latvia
Lithuania Dmytro Volyniuk Department of Polymer Chemistry and Technology, Kaunas University of Technology

Yu-Chiang, Chao

Chia-Chih, Chang

Department of Physics, National Taiwan Normal University

Department of Applied Chemistry, National Chiao Tung University

Since organic light-emitting diodes (OLEDs) are widely used in display and lighting technologies, there is a growing demand for efficient, inexpensive, and harmless OLED emitters. All-organic materials exhibiting thermally activated delayed fluorescence (TADF) are established as the most appropriate OLED emitters. Notably, they do not contain noble metals, they produce light by harvesting both singlet and triplet excitons generated under electrical excitation and they are appropriate for low-temperature device fabrication processes. Many efficient low-molar-mass TADF emitters have been developed while only few polymeric TADF emitters were reported. Namely polymeric emitters are required for low-cost solution-processable OLEDs. Long-term stability of such devices can be increased due to the increased morphological stability of polymer based light-emitting layers. However, efficiency of existing polymeric TADF emitters is still lower than that of low-molar-mass TADF emitters mainly due to the difficulties to achieve a small singlet–triplet energy splitting and to decrease the non-radiative internal conversion in high-molecular-weight materials.

To develop efficient polymeric TADF emitters for solution-processable OLEDs, we propose a strategy of controlling intermolecular and intramolecular charge-transfer characteristics in polymeric materials by exploiting hydrogen bonding.

The dopants will be functionalized with complementary hydrogen-bonding donor groups that can form multiple hydrogen bonds with the hydrogen-bonding acceptor pendant groups present along the polymer backbone. As a result, the power of self-sorting of donors and acceptors attached to the polymeric backbone will be exploited for decreasing singlet–triplet splitting and energy losses of potential TADF polymers. This strategy will be tested in the frame of the project allowing to generate a myriad of functional TADF polymer systems. Highlighting, the main objective of the project is to design and synthesize polymeric emitters with controllable thermally activated delayed fluorescence for solution-processable OLEDs and perovskite LEDs. Having such objective, the main tasks will include:

  • molecular design using quantum chemical calculations;
  • synthesis of potential monomers and polymers;
  • characterizations of the obtained products;
  • thermal, electrochemical, optical, photoelectrical and TADF analyses of new emitters;
  • OLED and perovskite LEDs fabrication and characterization.

Hybrid OLED-Perovskite LED will be also examined to explore the feasibility of realizing white light LED by combining the blue emission from the newly developed OLED with the orange-yellow light from the perovskite layer. The interdisciplinary consortium of the project have the required backgrounds to achieve the targets of the project.