Lithium doping of semiconducting organic charge transport materials

Parthasarathy, Gautam; Shen, Chongfei; Kahn, Antoine; Forrest, Stephen R.

doi:10.1063/1.1359161

Cited by 351 publications

(250 citation statements)

References 11 publications

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“…A similar gap state was observed in the UPS spectra of Lideposited BCP films. 25 Our data also show that the K 4s-derived band just below E F is missing in thick films. This suggests that the gap state at 0.6 eV is derived from electron transfer from K 4s to LUMO of BCP, whereas the higherlying gap state is due to split-off state of BCP HOMO ͑al-though the theoretical calculations are necessary for the detail assignment͒.…”

Section: Resultssupporting

confidence: 53%

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Level alignment of gap state at organic-metal interface

Aoki

Toyoshima

Kamada

et al. 2009

Journal of Applied Physics

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Electron emission spectra resulting from thermal collision of He ‫ء‬ ͑2 3 S͒ atoms with 2,9-demethyl-4,7-diphenyl-1,10-phenanthroline ͑BCP͒ films deposited on metal substrates were measured to characterize gap states emerged at the organic-metal interface. For BCP on Au, the gap state is originated from weak chemisorption and serves as a mediator of metal wave functions to the first layer. For BCP on K, organic-metal complex is formed by spontaneous diffusion, yielding the gap states delocalized over the film. In the interfacial region, all the gap state reveals an incommensurate shift with the valence band top of the film, indicating the breakdown of the Schottky-Mott model as evaluating the transport characteristics in organic-metal system.

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Section: Resultssupporting

confidence: 53%

“…The gap states have been observed in BCP films on low work function metals 23,24 and Li-doped BCP film. 25 The purpose of the present study is twofold. One is to identify two types of gap states by probing the local electronic states emerged at the topmost layer.…”

Section: Introductionmentioning

confidence: 99%

Level alignment of gap state at organic-metal interface

Aoki

Toyoshima

Kamada

et al. 2009

Journal of Applied Physics

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“…However, this inter-diffusion process between OS and TMO thin films sometimes can be underestimated, especially when depositing TMO on OS. Previous study indicates that, after depositing metal Li on OS, the diffusion depth of Li into OS can be up to 70 nm depending on the choice of the OS [30]. If similar process exists in TMO-on-OS structure, the mechanism for the improvement of the hole current should be revised.…”

Section: Introductionmentioning

confidence: 99%

Transition metal oxides on organic semiconductors

Zhao

Zhang

Liu

et al. 2014

Organic Electronics

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a b s t r a c tTransition metal oxides (TMOs) on organic semiconductors (OSs) structure has been widely used in inverted organic optoelectronic devices, including inverted organic light-emitting diodes (OLEDs) and inverted organic solar cells (OSCs), which can improve the stability of such devices as a result of improved protection of air sensitive cathode. However, most of these reports are focused on the anode modification effect of TMO and the nature of TMO-on-OS is not fully understood. Here we show that the OS on TMO forms a two-layer structure, where the interface mixing is minimized, while for TMO-on-OS, due to the obvious diffusion of TMO into the OS, a doping-layer structure is formed. This is evidenced by a series of optical and electrical studies. By studying the TMO diffusion depth in different OS, we found that this process is governed by the thermal property of the OS. The TMO tends to diffuse deeper into the OS with a lower evaporation temperature. It is shown that the TMO can diffuse more than 20 nm into the OS, depending on the thermal property of the OS. We also show that the TMO-on-OS structure can replace the commonly used OS with TMO doping structure, which is a big step toward in simplifying the fabrication process of the organic optoelectronic devices.

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“…Doping is an important technique to control the electrical properties of polymer layers: [9,10] it increases the conductivity by several orders of magnitude even at minimal doping concentration, [9,11,12] and decreases the charge injection barrier resulting from the position shift of Fermi level relative to the carrier level. [13][14][15] Recent research has demonstrated that molecule doping-induced tail state filling can also effectively suppress geminate charge recombination at donor-acceptor interface via charge transfer excitions in bulk heterjunction (BHJ) photovoltaic. [16] Another positive effect of doping is improvement of carrier mobility attributed to deep-trap filling.…”

Section: Introductionmentioning

confidence: 99%

Energetics at Doped Conjugated Polymer/Electrode Interfaces

Bao

Liu

Gao

et al. 2014

Adv Materials Inter

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Abstract:The energy level alignment at molecule-doped conjugated polymer/electrode interface is investigated. We find regular plots with a constant thickness-independent displacement away from the original energy level alignment behavior of the pristine polymer at low to intermediate level for molecule-doped conjugated polymer/conducting substrate interfaces.We proposed that two combined processes control the energy level alignment: (i) equilibration of the Fermi level due to oxidation (or reduction) of polymer sites at the interface as per the integer charge transfer model and (ii) a double dipole step induced by image charge from the dopant-polymer charge transfer complex that cause a shift of the work function. Such behavior is expected to hold for all low to intermediate level doped organic semiconductor systems.

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Lithium doping of semiconducting organic charge transport materials

Cited by 351 publications

References 11 publications

Level alignment of gap state at organic-metal interface

Level alignment of gap state at organic-metal interface

Transition metal oxides on organic semiconductors

Energetics at Doped Conjugated Polymer/Electrode Interfaces

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