TY  - JOUR
A1  - Raoufi, Meysam
A1  - Hörmann, Ulrich
A1  - Ligorio, Giovanni
A1  - Hildebrandt, Jana
A1  - Pätzel, Michael
A1  - Schultz, Thorsten
A1  - Perdigon-Toro, Lorena
A1  - Koch, Norbert
A1  - List-Kratochvil, Emil
A1  - Hecht, Stefan
A1  - Neher, Dieter
T1  - Simultaneous effect of ultraviolet radiation and surface modification on the work function and hole injection properties of ZnO thin films
JF  - Physica Status Solidi.  A , Applications and materials science
N2  - The combined effect of ultraviolet (UV) light soaking and self-assembled monolayer deposition on the work function (WF) of thin ZnO layers and on the efficiency of hole injection into the prototypical conjugated polymer poly(3-hexylthiophen-2,5-diyl) (P3HT) is systematically investigated. It is shown that the WF and injection efficiency depend strongly on the history of UV light exposure. Proper treatment of the ZnO layer enables ohmic hole injection into P3HT, demonstrating ZnO as a potential anode material for organic optoelectronic devices. The results also suggest that valid conclusions on the energy-level alignment at the ZnO/organic interfaces may only be drawn if the illumination history is precisely known and controlled. This is inherently problematic when comparing electronic data from ultraviolet photoelectron spectroscopy (UPS) measurements carried out under different or ill-defined illumination conditions.
KW  - charge injection across hybrid interfaces
KW  - energy-level alignments
KW  - hybrid metal oxides
KW  - organic interfaces
Y1  - 2020
U6  - https://doi.org/10.1002/pssa.201900876
SN  - 1862-6300
SN  - 1862-6319
VL  - 217
IS  - 5
SP  - 1
EP  - 6
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Lange, Ilja
A1  - Reiter, Sina
A1  - Kniepert, Juliane
A1  - Piersimoni, Fortunato
A1  - Paetzel, Michael
A1  - Hildebrandt, Jana
A1  - Brenner, Thomas J. K.
A1  - Hecht, Stefan
A1  - Neher, Dieter
T1  - Zinc oxide modified with benzylphosphonic acids as transparent electrodes in regular and inverted organic solar cell structures
JF  - Applied physics letters
N2  - An approach is presented to modify the work function of solution-processed sol-gel derived zinc oxide (ZnO) over an exceptionally wide range of more than 2.3 eV. This approach relies on the formation of dense and homogeneous self-assembled monolayers based on phosphonic acids with different dipole moments. This allows us to apply ZnO as charge selective bottom electrodes in either regular or inverted solar cell structures, using poly(3-hexylthiophene): phenyl-C71-butyric acid methyl ester as the active layer. These devices compete with or even surpass the performance of the reference on indium tin oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. Our findings highlight the potential of properly modified ZnO as electron or hole extracting electrodes in hybrid optoelectronic devices. (C) 2015 AIP Publishing LLC.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4916182
SN  - 0003-6951
SN  - 1077-3118
VL  - 106
IS  - 11
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Lange, Ilja
A1  - Reiter, Sina
A1  - Paetzel, Michael
A1  - Zykov, Anton
A1  - Nefedov, Alexei
A1  - Hildebrandt, Jana
A1  - Hecht, Stefan
A1  - Kowarik, Stefan
A1  - Woell, Christof
A1  - Heimel, Georg
A1  - Neher, Dieter
T1  - Tuning the work function of polar zinc oxide surfaces using modified phosphonic acid self-assembled monolayers
JF  - Advanced functional materials
N2  - Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self-assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole-injecting and electron-injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well-defined molecular monolayers.
KW  - ZnO
KW  - self-assembled monolayers
KW  - phosphonic acid
KW  - surface modification
KW  - electrodes
Y1  - 2014
U6  - https://doi.org/10.1002/adfm.201401493
SN  - 1616-301X
SN  - 1616-3028
VL  - 24
IS  - 44
SP  - 7014
EP  - 7024
PB  - Wiley-VCH
CY  - Weinheim
ER  -