Charge Recombination in Polaron Pairs: A Key Factor for Operational Stability of Blue-Phosphorescent Light-Emitting Devices

Alexey Odinokov, Alexey Osipov, Juwon Oh, Yu Kyung Moon, Soo Ghang Ihn, Hasup Lee, Inkoo Kim, Won Joon Son, Sangmo Kim, Dmitry Kravchuk, Jong Soo Kim, Joonghyuk Kim, Hyeonho Choi, Sunghan Kim, Wook Kim, Namheon Lee, Seongsoo Kang, Dongho Kim, Youngmin You, Alexander Yakubovich

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Irreversible chemical reactions are responsible for limited operational lifetime of organic light-emitting devices (OLEDs). These reactions are triggered by highly reactive polaron pairs present in the emissive layer of OLEDs. Fast recombination of the polaron pairs is, therefore, crucial for slow degradation and high stability of OLED materials. Here, a study of the formation and annihilation of close polaron pairs in binary mixtures of wide bandgap hosts and a series of blue-phosphorescent Ir(III) complex dopants, including two novel compounds, is reported. OLED devices containing doped light-emitting layer are fabricated, and their operational lifetimes are estimated. Although inaccessible in solid films, charge recombination kinetics inside the polaron pairs is measured in liquid solutions using nanosecond laser flash photolysis. Multiscale computer simulations are applied to connect experimental results in different media and predict recombination rates in the device, with proper account taken of the inner- and outersphere reorganization in nonpolar materials. Predicted rates correlate with measured operational lifetimes, which demonstrates the key role of polaron pairs in the OLED degradation process. The developed methodology is useful for the rational design of novel OLED materials with higher efficiency and stability.

Original languageEnglish
Article number2000028
JournalAdvanced Theory and Simulations
Issue number8
StatePublished - 1 Aug 2020


  • OLED degradation
  • electron transfer
  • molecular dynamics
  • radical ion pairs
  • reorganization energy


Dive into the research topics of 'Charge Recombination in Polaron Pairs: A Key Factor for Operational Stability of Blue-Phosphorescent Light-Emitting Devices'. Together they form a unique fingerprint.

Cite this