Final Report, Department of Energy, Office of Basic Energy Sciences, Luminescence in Conjugated Molecular Materials Under Sub-Bandgap Excitation, Period: Sept. 1, 2010-December 31, 2013.

So, F.

Technical Information Center Oak Ridge Tennessee

关键词: Luminescence;    Molecules;    Excitation;    Annihilation;    Bandgap;   

RP-ID  :  DE141130750

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

The objective of our recent DOE effort has been to study sub-bandgap electroluminescence using ZnO nanoparticles (NPs) as an electron transport layer. We found that when the polymer/NPs interface form a type-II heterojunction and hole transporting polymers such as MEH-PPV and MDMO-PPV, luminance was observed when a sub-bandgap voltage was applied to the device. When electron transport polymers were used, sub-bandgap electroluminescence was not observed. In addition to polymer light emitting diodes, we have also observed sub-bandgap electroluminescence in small molecule devices using rubrene as an emitter and fullerene as an electron transport layer. Previously, we used the Auger model to explain the luminescence at voltages below the bandgap voltages. With our recent data, we attribute the sub-bandgap EL is due to triplet-triplet annihilation (TTA) in rubrene originated from the formation of charge transfer excitons. Transient EL decay of sub-bandgap emission shows the characteristic of TTA. The presence of charge transfer states in this system is verified with electroabsorption measurements.