High Efficiency Exciplex Emission for Applications in Organic Light-Emitting Devices
DescriptionConsiderable attention has been focused in recent years for the use of exciplex emission as a simple means for spectral tuning and for producing white emitting organic light-emitting devices (OLEDs). However, the major problem in utilizing exciplex emission is its extremely low external quantum efficiency (ηext). For many years, exciplex emission has been considered to be useless for practical applications. However, the researchers recently reported an exciplex-based device with a high ηext of 4.0%. While this suggests that low efficiency is not an inherent problem of exciplex emission, the underlying physics for the unexpectedly high efficiency are still not clear. This project aims to identify important factors influencing exciplex emission and to provide physical insights for device engineering towards high efficiency exciplex emission. The researchers propose to study the effects of photoluminescence quantum yields of organic materials, relative mobilites and electron energy levels of the electron- and the hole- transporting materials which form the exciplex, width of the emission zone and interfacial electronic structures. The interplay of device efficiency and the electronic structures (including molecular level offsets, possible band bending, and chemical reactions) at the exciplex forming interface would be studied via photoelectron spectroscopy. The success of this project is expected to clarify physics involved in high efficiency exciplex emission, and to provide guidelines for material selection and development for exciplex-based OLEDs.
|Effective start/end date||1/10/08 → 29/05/12|