Unraveling the Fate of Host Excitons in Host-Guest Phosphorescent Organic Light-Emitting Diodes

Journal Article · Fri Apr 05 00:00:00 EDT 2019 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.9b02820· OSTI ID:1505181

Zhu, Tianyu ^[1]; Van Voorhis, Troy ^[2]

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1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Chemistry; Massachusetts Institute of Technology
2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Chemistry

Understanding energy and charge transfer mechanisms in host-guest systems is crucial for improving performance of organic light-emitting diodes (OLEDs), but it presents a theoretical challenge due to disordered molecular environment. Here, we address the fate of excitons that form on the host in a BTDF-Ir(ppy)₃ phosphorescent OLED through a QM/MM simulation. Our results demonstrate that triplet host excitons can be harvested through efficient energy transfer to the T₁ state of the guest allowed by excellent spectral overlap. Detailed analysis of the guest absorption spectrum uncovers that high-lying guest singlet states play a critical role in utilizing singlet host excitons. Furthermore, we investigate the process where host excitons break up and reform on the guest, and show it is unfavored owing to the high energy barrier. This work thus reveals energy transfer is the primary quenching mechanism for host excitons and highlights strategies for better host-guest design.

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: FG02-07ER46474
• OSTI ID: 1505181
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 16 Vol. 123; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE