Energy level alignment at a charge generation interface between 4,4′-bis(N-phenyl-1-naphthylamino)biphenyl and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile

2009 ◽  
Vol 94 (6) ◽  
pp. 063305 ◽  
Author(s):  
Yong-Ki Kim ◽  
Jeong Won Kim ◽  
Yongsup Park
Keyword(s):  
Energy Level ◽  
Charge Generation ◽  
Energy Level Alignment ◽  
A Charge

The role of gap states on energy level alignment at an α-NPD/HAT(CN) 6 charge generation interface

2015 ◽  
Vol 24 ◽  
pp. 120-124 ◽  
Author(s):  
Jin-Peng Yang ◽  
Fabio Bussolotti ◽  
Yan-Qing Li ◽  
Xiang-Hua Zeng ◽  
Satoshi Kera ◽  
...  
Keyword(s):  
Energy Level ◽  
Charge Generation ◽  
Energy Level Alignment ◽  
Gap States

Interaction and Energy Level Alignment at Interfaces between Pentacene and Low Work Function Metals

2001 ◽  
Vol 708 ◽  
Author(s):  
N. Koch ◽  
J. Ghijsen ◽  
R. Ruiz ◽  
J. Pflaum ◽  
R. L. Johnson ◽  
...  
Keyword(s):  
Energy Level ◽  
Alkali Metal ◽  
Molecular Orbital ◽  
Organic Material ◽  
Alkali Metals ◽  
Energy Gap ◽  
Emission Feature ◽  
Photoemission Spectroscopy ◽  
Energy Level Alignment ◽  
A Charge

ABSTRACTA number of low workfunction metals (samarium, alkali metals) were deposited onto vacuum sublimed thin films of pentacene. The change in the valence electronic structure of the organic material was studied by in situ ultraviolet photoemission spectroscopy (UPS). Alkali metal intercalation leads to the appearance of a new photoemission feature within the pentacene energy gap, due to a charge transfer from the alkali atoms to the lowest unoccupied molecular orbital (LUMO) of the organic material. The energy spacing between this emission feature and the relaxed highest occupied molecular orbital (HOMO) of the pristine molecule is 1 eV. From X-ray photoemission spectroscopy core level analysis, we estimate a concentration ratio of two alkali metal atoms per pentacene molecule at maximum intercalation level, leading to a complete filling of the LUMO. This is consistent with the results from UPS that the new emission is always observed below the Fermi-level. Samarium is found to exhibit a more subtle interaction with pentacene: the molecular orbitals remain almost unperturbed upon Sm deposition. The resulting energy level alignment at this interface seems to be very favorable for the injection of electrons from Sm into pentacene, as the HOMO-onset is found at 1.8 eV below the metal Fermi edge. This value is close to the 2.2 eV HOMO-LUMO gap of pentacene measured by UPS and inverse photoemission spectroscopy, thus corresponding to a small electron injection barrier.

scholarly journals Ultrafast electron and hole transfer in bulk heterojunctions of low-bandgap polymers

2016 ◽  
Vol 4 (1) ◽  
Author(s):  
Oleg V. Kozlov ◽  
Vlad G. Pavelyev ◽  
Hilde D. de Gier ◽  
Remco W. A. Havenith ◽  
Paul H.M. van Loosdrecht ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Energy Level ◽  
Charge Separation ◽  
Density Functional ◽  
Free Charge ◽  
Charge Generation ◽  
Hole Transfer ◽  
Low Bandgap ◽  
Transfer Processes ◽  
Energy Level Alignment

AbstractIn modern bulk heterojunction (BHJ) organic solar cells, blends of low-bandgap polymer and [70]PCBM acceptor are used in the active layer. In this combination, the polymer absorbs photons from the red and near-IR parts of the solar spectrum, while the blue and near-UV photons are harvested by [70]PCBM. As a result, both electron transfer from polymer to [70]PCBM and hole transfer from [70]PCBM to polymer are of utmost importance in free charge generation and have to be optimized simultaneously. Here we study electron and hole transfer processes in BHJ blends of two low-bandgap polymers, BTT-DPP and PCPDTBT, by ultrafast photoinduced spectroscopy (PIA). By tracking the PIA dynamics, we observed substantially different charge separation pathways in BHJs of the two polymers with [70]PCBM. From the photoinduced anisotropy dynamics, we demonstrated that in the PCPDTBT:[70]PCBM system both electron and hole transfer processes are highly efficient, while in the BTTBPP:[ 70]PCBM electron transfer is blocked due to the unfortunate energy level alignment leaving hole transfer the only pathway to free charge generation. Calculations at the density functional theory level are used to gain more insight into our findings. The presented results highlight the importance of the energy level alignment on the charge separation process.

Sign in / Sign up

Export Citation Format

Share Document