Issue 31, 2014

Studying the influence of triplet deactivation on the singlet–triplet inter-conversion in intra-molecular charge-transfer fluorescence-based OLEDs by magneto-electroluminescence

Abstract

The forward conversion from singlets to triplets and backward conversion from triplets to singlets are both possible in charge-transfer (CT) fluorescence-based organic light-emitting devices (OLEDs) due to the small energy difference between singlet and triplet CT states. Thus, clarifying factors affecting the direction of the conversion is important to obtain highly efficient OLEDs based on thermally activated delayed fluorescence (TADF). Here, we investigated the inter-conversion between singlets and triplets in a CT fluorescence-based OLED via magneto-electroluminescence (MEL) measurements. The values of MELs turned from negative to positive with the increase in driving voltage and electric stressing time, indicating that the direction of the conversion was changed. Both the increase in driving voltage and stressing time can cause the quenching of triplets through triplet–triplet annihilation and triplet–trap interaction, respectively. Thus, the decreased population ratio of triplet to singlet induces the change of the direction of inter-conversion. Our results demonstrate that the singlet–triplet inter-conversion is a dynamic process, and the deactivation rates of singlet and triplet determine the inter-conversion direction.

Graphical abstract: Studying the influence of triplet deactivation on the singlet–triplet inter-conversion in intra-molecular charge-transfer fluorescence-based OLEDs by magneto-electroluminescence

Supplementary files

Article information

Article type
Paper
Submitted
30 Apr 2014
Accepted
02 Jun 2014
First published
04 Jun 2014

J. Mater. Chem. C, 2014,2, 6264-6268

Author version available

Studying the influence of triplet deactivation on the singlet–triplet inter-conversion in intra-molecular charge-transfer fluorescence-based OLEDs by magneto-electroluminescence

Q. Peng, A. Li, Y. Fan, P. Chen and F. Li, J. Mater. Chem. C, 2014, 2, 6264 DOI: 10.1039/C4TC00885E

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