Self-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopant
In contrast to p-dopants, highly efficient molecular n-dopants are prone to degradation in air due to their low ionization potentials, limiting the processing conditions of doped functional organic devices. In this contribution, we investigate the air-stability of pure films of the n-dopant tetrakis...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Language: | English |
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Wiley
2013
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| _version_ | 1826264933926436864 |
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| author | Tietze, M Wölzl, F Menke, T Fischer, A Riede, M Leo, K Lüssem, B |
| author_facet | Tietze, M Wölzl, F Menke, T Fischer, A Riede, M Leo, K Lüssem, B |
| author_sort | Tietze, M |
| collection | OXFORD |
| description | In contrast to p-dopants, highly efficient molecular n-dopants are prone to degradation in air due to their low ionization potentials, limiting the processing conditions of doped functional organic devices. In this contribution, we investigate the air-stability of pure films of the n-dopant tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato)ditungsten(II) (W<sub>2</sub>(hpp)<sub>4</sub>) and of C<sub>60</sub> layers doped by W<sub>2</sub>(hpp)<sub>4</sub>. We find that 1/3 of the initial conductivity of the doped C<sub>60</sub> thin films can be restored by thermal annealing in vacuum after a drop by 5 orders of magnitude upon air exposure. Furthermore, we show by ultraviolet photoelectron spectroscopy (UPS) and Seebeck measurements that the Fermi level shift toward the lowest unoccupied molecular orbital (LUMO) of C<sub>60</sub> remains after air exposure, clearly indicating a conservation of n-doping. We explain these findings by a down-shift of the W<sub>2</sub>(hpp)<sub>4</sub> energy levels upon charge-transfer to a host material with deeper lying energy-levels, facilitating a protection against oxidation in air. Consequently, the observed recovery of the conductivity can be understood in terms of a self-passivation of the molecular n-doping. Hence, an application of highly efficient n-doped thin films in functional organic devices handled even under ambient conditions during fabrication is feasible. © 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim. |
| first_indexed | 2024-03-06T20:15:44Z |
| format | Journal article |
| id | oxford-uuid:2c16ab11-9144-454d-af3b-bcd786cb3b00 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T20:15:44Z |
| publishDate | 2013 |
| publisher | Wiley |
| record_format | dspace |
| spelling | oxford-uuid:2c16ab11-9144-454d-af3b-bcd786cb3b002022-03-26T12:34:52ZSelf-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopantJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:2c16ab11-9144-454d-af3b-bcd786cb3b00EnglishSymplectic Elements at OxfordWiley2013Tietze, MWölzl, FMenke, TFischer, ARiede, MLeo, KLüssem, BIn contrast to p-dopants, highly efficient molecular n-dopants are prone to degradation in air due to their low ionization potentials, limiting the processing conditions of doped functional organic devices. In this contribution, we investigate the air-stability of pure films of the n-dopant tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato)ditungsten(II) (W<sub>2</sub>(hpp)<sub>4</sub>) and of C<sub>60</sub> layers doped by W<sub>2</sub>(hpp)<sub>4</sub>. We find that 1/3 of the initial conductivity of the doped C<sub>60</sub> thin films can be restored by thermal annealing in vacuum after a drop by 5 orders of magnitude upon air exposure. Furthermore, we show by ultraviolet photoelectron spectroscopy (UPS) and Seebeck measurements that the Fermi level shift toward the lowest unoccupied molecular orbital (LUMO) of C<sub>60</sub> remains after air exposure, clearly indicating a conservation of n-doping. We explain these findings by a down-shift of the W<sub>2</sub>(hpp)<sub>4</sub> energy levels upon charge-transfer to a host material with deeper lying energy-levels, facilitating a protection against oxidation in air. Consequently, the observed recovery of the conductivity can be understood in terms of a self-passivation of the molecular n-doping. Hence, an application of highly efficient n-doped thin films in functional organic devices handled even under ambient conditions during fabrication is feasible. © 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim. |
| spellingShingle | Tietze, M Wölzl, F Menke, T Fischer, A Riede, M Leo, K Lüssem, B Self-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopant |
| title | Self-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopant |
| title_full | Self-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopant |
| title_fullStr | Self-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopant |
| title_full_unstemmed | Self-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopant |
| title_short | Self-passivation of molecular n-type doping during air exposure using a highly efficient air-instable dopant |
| title_sort | self passivation of molecular n type doping during air exposure using a highly efficient air instable dopant |
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