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Oct. 14, 2016 {Finished} The 125th Conference on Organic Electronics

 

Time/Date:  15:30 ~ 16:30   Friday   Oct 14, 2016

 

Location:   Meeting Room, 5F, Building No.11

 

Lecturer:   Prof Yuguang Ma

                     (State Key Laboratory of Luminescent Materials and Devices, South China University of Technology)

 

Subject:    High-lying “Hot” Excitons for OLEDs

 

                

When a singlet state(S) nonradiatively passes to a triplet state(T), or conversely a T transitions to a S, that process is known as intersystem crossing(ISC, S to T) or RISC(T to S). Because the spin of the excited electron is reversed, the time scale of ISC is relative slow with the order of 10−8 to 10−3 s, one of the slowest forms of relaxation. As a result, the probability of this process occurring is sufficiently low. In some case this process can be accelerated when the vibrational levels of both S and T states overlap or the spin/orbital interactions in such molecules are substantial. In heavy-atom molecules with strong spin-orbit coupling, ISC become more favourable, and the heavy metal complexes behavior strong phosphorescence for highly efficient OLEDs. In very few case, RISC from lowest triplet states (T1) to lowest singlet states (S1) can become a dominated process, typically as the thermally-activated delayed fluorescence (TADF) and triplet-triplet annihilation (TTA), but it is great challenging to obtain highly exciton utilization efficiency (ηr) and fluorescence efficiency (ηPL). In the end 1969, some aromatic compounds were found that the RISC can occur from the high-lying triplet energy levels to the singlet manifold(Tn (n>1) → S1)1, but the efficiency of such delayed fluorescence is too low to find a suitable application. Here, we innovatively rejuvenated this “sleeping” photophysical process by utilizing it to break the exciton statistics limit in OLEDs. Arduous efforts are made to developing fluorescent materials with combination of high photoluminescence efficiency and effective RISC through appropriate molecular design in a series of donor-acceptor (D-A) material systems. The experimental and theoretical results indicate that these materials exhibit hybridized local and charge-transfer excited state (HLCT), which achieve a combination of the high radiation from local excited state (LE) and the high Tm→Sn (m≥2, n≥1) conversion along charge-transfer excited state (CT). As expected, the devices exhibited favorable external quantum efficiency (EQE) and low roll-off, and especially the exciton utilization efficiency exceeding the limit of 25%.2,3..

 

[1] R.A.Keller, Chem. Phys. Lett., 3(1969), 27. [2] L.Yao, B.Yang, Y.G. Ma, Angew. Chem. Int. Ed., 53(2014), 2119. [3] L.Yao, B.Yang, Y.G. Ma, Sci. China. Chem., 57(2014), 335.

 

 

 

 

2016 List of Events

Nov. 30, 2016
{Finished} A seminar about Analysis (Toray Research Center)
Nov. 01, 2016
{Finished} The 128th Conference on Organic Electronics
Nov. 01, 2016
{Finished} The 127th Conference on Organic Electronics
Oct. 18, 2016
{Finished} The 126th Conference on Organic Electronics
Oct. 14, 2016
{Finished} The 125th Conference on Organic Electronics
Oct. 03, 2016
{Finished} The 124th Conference on Organic Electronics
Jun. 07, 2016
{Finished} The 123th Conference on Organic Electronics
May 25, 2016
{Finished} The 122th Conference on Organic Electronics
Apr. 28, 2016
{Finished} The 121th Conference on Organic Electronics
Apr. 27, 2016
{Finished} The 120th Conference on Organic Electronics
Apr. 27, 2016
{Finished} The 119th Conference on Organic Electronics
Apr. 26, 2016
{Finished} The 118th Conference on Organic Electronics
Apr. 20, 2016
{Finished} The 117th Conference on Organic Electronics
Apr. 18, 2016
{Finished} (4/17) Yamagata University and Iide Town had a joint event, "Experience! The Future of Iide Machi".
Mar. 14, 2016
{Finished} (3/11) Organic Electronics Workshop - 5th Different Industries Exchange Meeting - has been held on March 11.
Mar. 07, 2016
{Finished} (3/11) An opening ceremony and a sneak preview of a new building, Frontier Center for Organic Materials, has been held on March, 11.
Feb. 23, 2016
{Finished} The 116th Conference on Organic Electronics
Jan. 26, 2016
{Finished} (1/26) "4th Germany-Japan Joint Workshop" has been held in Yonezawa on January 26th 2016.
Jan. 25, 2016
{Finished} (1/25) "4th Germany-Japan Joint Workshop" -Organic Electronics and Nano Materials for Energy- has been held in Yonezawa on January 25th 2016.
Jan. 21, 2016
{Finished} (1/25) Prof Tokito will have a keynote speech in 4th Germany-Japan Joint Workshop "Organic Electronics and Nano Materials for Energy" on January 25, 2016 in Tokyo.
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