| 1. |
- Fabiano, Simone, et al.
(författare)
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Charge transport orthogonality in all-polymer blend transistors, diodes, and solar cells
- 2014
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Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlag. - 1614-6832 .- 1614-6840. ; 4:6, s. 1301409-
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Tidskriftsartikel (refereegranskat)abstract
- Polymer aggregation and phase separation of polymer-polymer blends are effectively tuned from self-stratified to laterally phase-separated by adjusting the relative solubility of the two polymers in the mixture. This is found to dramatically alter the charge transport characteristics from a preferential in-plane to an out-of-plane direction, revealing the critical dependence of the resulting device performance on the film morphology and structure of the active layer. © 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.
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| 2. |
- Fabiano, Simone, et al.
(författare)
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Effect of Gate Electrode Work-Function on Source Charge Injection in Electrolyte-Gated Organic Field-Effect Transistors
- 2014
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 24:5, s. 695-700
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Tidskriftsartikel (refereegranskat)abstract
- Systematic investigation of the contact resistance in electrolyte-gated organic field-effect transistors (OFETs) demonstrates a dependence of source charge injection versus gate electrode work function. This analysis reveals contact-limitations at the source metal-semiconductor interface and shows that the contact resistance increases as low work function metals are used as the gate electrode. These findings are attributed to the establishment of a built-in potential that is high enough to prevent the Fermi-level pinning at the metal-organic interface. This results in an unfavorable energetic alignment of the source electrode with the valence band of the organic semiconductor. Since the operating voltage in the electrolyte-gated devices is on the same order as the variation of the work functions, it is possible to tune the contact resistance over more than one order of magnitude by varying the gate metal.
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| 3. |
- Fabiano, Simone, et al.
(författare)
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Ferroelectric Polarization Induces Electric Double Layer Bistability in Electrolyte-Gated Field-Effect Transistors
- 2014
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 6:1, s. 438-442
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Tidskriftsartikel (refereegranskat)abstract
- The dense surface charges expressed by a ferroelectric polymeric thin film induce ion displacement within a polyelectrolyte layer and vice versa. This is because the density of dipoles along the surface of the ferroelectric thin film and its polarization switching time matches that of the (Helmholtz) electric double layers formed at the ferroelectric/polyelectrolyte and polyelectrolyte/semiconductor interfaces. This combination of materials allows for introducing hysteresis effects in the capacitance of an electric double layer capacitor. The latter is advantageously used to control the charge accumulation in the semiconductor channel of an organic field-effect transistor. The resulting memory transistors can be written at a gate voltage of around 7 V and read out at a drain voltage as low as 50 mV. The technological implication of this large. difference between write and read-out voltages lies in the non-destructive reading of this ferroelectric memory.
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| 4. |
- Fabiano, Simone, et al.
(författare)
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Poly(ethylene imine) impurities induce n-doping reaction in organic (semi)conductors
- 2014
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Ingår i: Advanced Materials. - : Wiley-VCH Verlagsgesellschaft. - 0935-9648 .- 1521-4095. ; 26:34, s. 6000-6006
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Tidskriftsartikel (refereegranskat)abstract
- Volatile impurities contained in polyethyleneimine (PEI), and identified as ethyleneimine dimers and trimers, are reported. These N-based molecules show a strong reducing character, as demonstrated by the change in electrical conductivity of organic (semi) conductors exposed to the PEI vapor. The results prove that electron transfer rather than a dipole effect at the electrode interface is the origin of the work-function modification by the PEI-based layers.
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| 5. |
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| 6. |
- Sinno, Hiam, 1983-, et al.
(författare)
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Bias stress effect in inverters based on polyelectrolyte-gated organic field effect transistors
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Prolonged gate bias application causes undesirable operational instabilities in organic transistors involving threshold voltage shift and drain current degradation; an effect known as bias stress. In this paper, we report how this instability is manifested in inverter circuits based on polyelectrolytegated p-type organic field effect transistors (EGOFETs) operating at low voltage. We find that bias stress causes a significant, but recoverable, shift in inverter switching threshold voltage. Measurements with two different polyelectrolytes reveal significant differences in the stressing and recovery behaviour, which is ascribed to the distinct nature of the ion conductive groups in the polyelectrolyte. Moreover, we report a large influence of illumination on the recovery process for one of the polyelectrolytes but not for the other, which demonstrates the need to characterize bias stress behavior for each new materials combination.
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| 7. |
- Sinno, Hiam, 1983-, et al.
(författare)
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Bias stress effect in polyelectrolyte-gated organic field-effect transistors
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:11
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Tidskriftsartikel (refereegranskat)abstract
- A main factor contributing to bias stress instability in organic transistors is charge trapping of mobile carriers near the gate insulator-semiconductor interface into localized electronic states. In this paper, we study the bias stress behavior in low-voltage (p-type) polyelectrolyte-gated organic field effect transistors (EGOFETs) at various temperatures. Stressing and recovery in these EGOFETs are found to occur six orders of magntiude faster than typical bias stress/recovery reported for dielectric-gated OFETs. The mechanism proposed for EGOFETs involves an electron transfer reaction between water and the charged semiconductor channel that promotes the creation of extra protons diffusing into the polyelectrolyte.
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| 8. |
- Zhen, Hongyu, et al.
(författare)
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Solution-processed bulk-heterojunction organic solar cells employing Ir complexes as electron donors
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 2:31, s. 12390-12396
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Tidskriftsartikel (refereegranskat)abstract
- To explore enhancing photocurrent in organic solar cells (OSCs) via harvesting triplet excitons, two novel bicycloiridium complexes (R-1 and R-2) are designed and synthesized. Conventional bulk-heterojunction triplet OSCs are solution processed using R-1 or R-2 as sole electron donors and phenyl-C-71-butyric acid methyl ester (PC71BM) as the electron acceptor. A decent short circuit current (J(sc)) of 6.5 mA cm(-2) is achieved though the overlap between the absorption spectrum (with similar to 550 nm absorption onset) of R-2 and the solar flux is relatively small. With an open circuit voltage of 0.74 V and a fill factor of 0.42, an encouraging power conversion efficiency of 2.0% is achieved in the OSCs based on R-2 and PC71BM without any processing additives and post-treatments. Our preliminary result demonstrates the possibility of utilizing Ir complexes as sole electron donors in OSCs, which extends available soluble small molecules for OSCs.
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