Electron affinities of organic materials used for organic lightemitting diodes : A low-energy inverse photoemission study

The electron affinity (EA) of an organic semiconductor is a measure of the electron transportlevel. Although reliable values of the EA are required for designing the device architectureof organic light-emitting diodes (OLED), there were no appropriate methods. Recentlywe have developed low-energy inverse photoemission spectroscopy which enables us todetermine the EA of organic materials in solid with the precision required for research ofOLED. Using this new technique, we precisely determined EA of typical OLED materials,TCTA, CBP, Ir(ppy)3, BCP, Alq3 and Liq as well as a newly developed dopant 4CzIPN. Theobtained electron affinities are generally smaller by about 1 eV than the commonlybelieved values urging the reconsideration of the electron injection/transport mechanismsin OLED. We also compare EAs determined by various experimental and calculationmethods for 29 materials. The results show that the reduction potential gives a reasonableestimate rather than the optical gap and ionization energy.

https://opac.ll.chiba-u.jp/da/curator/100080/

https://opac.ll.chiba-u.jp/da/curator/100080/ElectronAffinitiesofOrganicMaterials.pdf

Elsevier

Journal Article

AA11621763

Organic Electronics

20

24

30

2015-02-04

https://doi.org/10.1016/j.orgel.2015.01.037

eng

http://dx.doi.org/10.1016/j.orgel.2015.01.037

author