at Google ScholarTitle data
Stankevych, Andrei ; Vakhnin, Alexander ; Andrienko, Denis ; Paterson, Leanne ; Genoe, Jan ; Fishchuk, Ivan ; Bässler, Heinz ; Köhler, Anna ; Kadashchuk, Andrey:
Density of States of OLED Host Materials from Thermally Stimulated Luminescence.
In: Physical Review Applied.
Vol. 15
(2021)
Issue 4
.
- 044050.
ISSN 2331-7019
DOI: https://doi.org/10.1103/PhysRevApplied.15.044050
Abstract in another language
The electronic density of states (DOS) plays a central role in controlling the charge-carrier transport in amorphous organic semiconductors, while its accurate determination is still a challenging task. We apply the low-temperature fractional thermally stimulated luminescence (TSL) technique to determine the DOS of pristine amorphous films of organic light-emitting diode (OLED) host materials. The DOS width is determined for two series of hosts, namely, (i) carbazole-biphenyl derivatives, 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP), 3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl (mCBP), and 3′,5-di(9H-carbazol-9-yl)-[1,1′-biphenyl]-3-carbonitrile (mCBP-CN), and (ii) carbazole-phenyl (CP) derivatives, 1,3-bis(N-carbazolyl)benzene (mCP) and 9-[3-(9H-carbazol-9-yl)phenyl]-9H-carbazole-3-carbonitrile (mCP-CN). TSL originates from radiative recombination of charge carriers thermally released from the lower-energy part of the intrinsic DOS that causes charge trapping at very low temperatures. We find that the intrinsic DOS can be approximated by a Gaussian distribution, with a deep exponential tail accompanying this distribution in CBP and mCBP films. The DOS profile broadens with increasing molecular dipole moments, varying from 0 to 6 D, in a similar manner within each series, in line with the dipolar disorder model. The same molecular dipole moment, however, leads to a broader DOS of CP compared with CBP derivatives. Using computer simulations, we attribute the difference between the series to a smaller polarizability of cations in CP derivatives, leading to weaker screening of the electrostatic disorder by induction. These results demonstrate that the low-temperature TSL technique can be used as an efficient experimental tool for probing the DOS in small-molecule OLED materials.
Further data
| Item Type: | Article in a journal |
|---|---|
| Refereed: | Yes |
| Institutions of the University: | Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Chair Experimental Physics II - Optoelectronics of Soft Matter Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Chair Experimental Physics II - Optoelectronics of Soft Matter > Chair Experimental Physics II - Optoelectronics of Soft Matter - Univ.-Prof. Dr. Anna Köhler Faculties Faculties > Faculty of Mathematics, Physics und Computer Science |
| Result of work at the UBT: | Yes |
| DDC Subjects: | 500 Science > 530 Physics |
| Date Deposited: | 06 May 2021 07:10 |
| Last Modified: | 15 Aug 2023 06:52 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/65103 |