Leuco Crystal Violet as a Dopant for n-Doping of Organic Thin Films of Fullerene C<sub>60</sub>

Li, Fenghong; Werner, Ansgar; Pfeiffer, Martin; Leo, Karl; Liu, Xianjie

doi:10.1021/jp0478615

Cited by 119 publications

(122 citation statements)

References 41 publications

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“…[ 1,10 ] Hence, research on the development of air stable n-dopant compounds has been actively pursued. In these approaches, the actual n-dopant is either preserved within a precursor molecule, [11][12][13][14][15] or present as the corresponding dimer with suffi cient low energy levels to resist oxidation. [16][17][18][19][20] In all of these cases, n-type doping of fullerene fi lms, i.e., [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) or C 60 (electron affi nity EA = 4.0 eV), was demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Passivation of Molecular n‐Doping: Exploring the Limits of Air Stability

Tietze

Rose

Schwarze

et al. 2016

Adv Funct Materials

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Molecular doping is a key technique for fl exible and low-cost organic complementary semiconductor technologies that requires both effi cient and stable p-and n-type doping. However, in contrast to molecular p-dopants, highly effi cient n-type dopants are commonly sensitive to rapid degradation in air due to their low ionization energies ( IE s) required for electron donation, e.g., IE = 2.4 eV for tetrakis(1,3,4,6,7,8-hexahydro-2H -pyrimido[1,2-a ]pyrimidinato) ditungsten(II) (W 2 (hpp) 4 ). Here, the air stability of various host:W 2 (hpp) 4 combinations is compared by conductivity measurements and photoemission spectroscopy. A partial passivation of the n-doping against degradation is found, with this effect identifi ed to depend on the specifi c energy levels of the host material. Since host-W 2 (hpp) 4 electronic wavefunction hybridization is unlikely due to confi nement of the dopant highest occupied molecular orbital (HOMO) to its molecular center, this fi nding is explained via stabilization of the dopant by single-electron transfer to a host material whose energy levels are suffi ciently low for avoiding further charge transfer to oxygen-water complexes. Our results show the feasibility of temporarily handling n-doped organic thin fi lms in air, e.g., during structuring of organic fi eld effect transistors (OFETs) by lithography.

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Section: Introductionmentioning

confidence: 99%

Passivation of Molecular n‐Doping: Exploring the Limits of Air Stability

Tietze

Rose

Schwarze

et al. 2016

Adv Funct Materials

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“…At an even higher doping thickness, the electron mobility is reduced. We attribute this reduction to both charge carrier scattering at high doping concentrations (42,43) and the tendency of o-MeO-DMBI to aggregate (33,34) as shown in the AFM images of SI Appendix, Fig. S2, which may perturb the morphology of the underlying layers and tube−tube contacts, although the exact origin has not been studied in detail.…”

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confidence: 99%

Tuning the threshold voltage of carbon nanotube transistors by n-type molecular doping for robust and flexible complementary circuits

Wang

Wei

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

189

174

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Tuning the threshold voltage of a transistor is crucial for realizing robust digital circuits. For silicon transistors, the threshold voltage can be accurately controlled by doping. However, it remains challenging to tune the threshold voltage of single-wall nanotube (SWNT) thin-film transistors. Here, we report a facile method to controllably n-dope SWNTs using 1H-benzoimidazole derivatives processed via either solution coating or vacuum deposition. The threshold voltages of our polythiophene-sorted SWNT thin-film transistors can be tuned accurately and continuously over a wide range. Photoelectron spectroscopy measurements confirmed that the SWNT Fermi level shifted to the conduction band edge with increasing doping concentration. Using this doping approach, we proceeded to fabricate SWNT complementary inverters by inkjet printing of the dopants. We observed an unprecedented noise margin of 28 V at V DD = 80 V (70% of 1/2V DD ) and a gain of 85. Additionally, robust SWNT complementary metal−oxide−semiconductor inverter (noise margin 72% of 1/2V DD ) and logic gates with rail-torail output voltage swing and subnanowatt power consumption were fabricated onto a highly flexible substrate. nanomaterials | n-doping | inkjet-printed | CMOS circuit F lexible electronics have attracted increasing attention recently due to the plethora of possible and realized applications in radio-frequency identification cards (1, 2), flexible displays (3, 4), and digital processors (5). Solution-processed single-walled carbon nanotubes (SWNTs) are a promising candidate for flexible circuits due to their high charge carrier mobility (6), excellent flexibility/stretchability (7-9), and their compatibility with lowcost, large-area manufacturing processes, such as printing (1, 10) of SWNTs. Their applications in thin-film transistors (TFTs) and integrated logic circuits (11-14) have been demonstrated. However, to achieve robust digital circuits with high immunity against the influence of electronic noise in the system, it is important to be able to control the specific value of the threshold voltage of a transistor during the fabrication process (15,16). This is because transistor threshold voltage determines the input voltage at which a circuit switches between two logic states (trip voltage of an inverter). When the trip voltage is half of the supply voltage, the circuit has the largest noise margin, which is a quantitative measure of the immunity of a logic circuit against noise and a figure of merit to characterize the robustness of the circuit (17, 18). If threshold voltage cannot be controlled during the fabrication process, the resulting circuit might not work reliably due to the electrical noise that is always present in the system. Because SWNTs have ambipolar electrical transport properties (19), accurately tuning the threshold voltage permits the construction of complementary metal−oxide−semiconductor (CMOS) circuits that use both the p-type and n-type character of SWNTs. The advantages of CMOS circuits compared with unipolar ...

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“…In polymer, doping process involves both oxidation and reduction processes [25][26][27]. The first method involves exposing a polymer to an oxidant such as iodine or bromine or a reluctant such as alkali metals.…”

Section: The Doping Conceptmentioning

confidence: 99%