Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps

Mei, Yaochuan; Diemer, Peter J.; Niazi, Muhammad Rizwan; Hallani, Rawad K.; Jarolimek, Karol; Day, Cyn­thia S.; Risko, Chad; Anthony, John E.; Amassian, Aram; Jurchescu, Oana D.

doi:10.1073/pnas.1705164114

Cited by 82 publications

(80 citation statements)

References 99 publications

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“…We minimized the scattering processes at the semiconductor/dielectric interface by employing a structure with air‐gap dielectric, as described in detail in Section 4. This interface is free of polaronic effects and strain, but it is not exempt from the trapping resulting from imperfections at the crystal surface. Crystal step edges present on the surfaces of organic semiconductors single crystal were found to be trapping sites for the charges accumulated at the interface between the crystal and the dielectric .…”

Section: Resultsmentioning

confidence: 99%

Charge‐Transport Properties of F₆TNAP‐Based Charge‐Transfer Cocrystals

Dasari

Wang

Wiscons

et al. 2019

Adv Funct Materials

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The crystal structures of the charge-transfer (CT) cocrystals formed by the π-electron acceptor 1,3,4,5,7,8-hexafluoro-11,11,12,12-tetracyanonaphtho-2,6-quinodimethane (F 6 TNAP) with the planar π-electron-donor molecules triphenylene (TP), benzo[b]benzo[4,5]thieno[2,3-d]thiophene (BTBT), benzo[1,2-b:4,5-b′]dithiophene (BDT), pyrene (PY), anthracene (ANT), and carbazole (CBZ) have been determined using single-crystal X-ray diffraction (SCXRD), along with those of two polymorphs of F 6 TNAP. All six cocrystals exhibit 1:1 donor/acceptor stoichiometry and adopt mixed-stacking motifs. Cocrystals based on BTBT and CBZ π-electron donor molecules exhibit brickwork packing, while the other four CT cocrystals show herringbone-type crystal packing. Infrared spectroscopy, molecular geometries determined by SCXRD, and electronic structure calculations indicate that the extent of ground-state CT in each cocrystal is small. Density functional theory calculations predict large conduction bandwidths and, consequently, low effective masses for electrons for all six CT cocrystals, while the TP-, BDT-, and PYbased cocrystals are also predicted to have large valence bandwidths and low effective masses for holes. Charge-carrier mobility values are obtained from space-charge limited current (SCLC) measurements and field-effect transistor measurements, with values exceeding 1 cm 2 V −1 s −1 being estimated from SCLC measurements for BTBT:F 6 TNAP and CBZ:F 6 TNAP cocrystals. exhibit properties distinct from those of their individual components. In chargetransfer (CT) cocrystals, one component acts as an π-electron donor (D) and another component acts as a π-electron acceptor (A), and both are typically planar molecules in order to facilitate CT interactions in the solid state. Two major types of molecular stacking motifs are found in CT crystals with 1:1 stoichiometry: mixed stacks, in which D and A molecules alternate along the stacking direction, -D-A-D-A, and segregated stacks, in which donor and acceptor molecules form separate stacks, -D-D-D-and -A-A-A. [1][2][3] When free of disorder, metallic conductivities can be obtained along the stacking direction of CT cocrystals that form segregated stacks and that exhibit extents of CT approximately midway (ρ = ca. 0.5) between the completely neutral (ρ = 0) and fully ionic (ρ = 1) limits. [1][2][3][4] On the other hand, CT cocrystals that consist of mixed stacks generally behave as semiconductors or insulators. [3,5] Recently there has been increasing interest in the semiconducting [6][7][8][9][10][11][12][13][14][15][16][17][18] and photoconductive [19][20][21] properties of mixed-stack cocrystals. Large charge-carrier mobility values, µ, have been reported for several examples using space-charge limited current (SCLC) or field-effect transistor (FET) measurements, includingThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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Section: Resultsmentioning

confidence: 99%

Charge‐Transport Properties of F₆TNAP‐Based Charge‐Transfer Cocrystals

Dasari

Wang

Wiscons

et al. 2019

Adv Funct Materials

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“…The structure of these two packing modes can be deduced by combining the results of 1 H and 19 F MAS NMR with further 1 H- 13 Since for every DPP and F4 unit two Th units are present in the polymer chain, the slip can occur in two directions ( Figure 5e) leading to the formation of either packing mode II or III. Interestingly, packing mode II retains point reflection symmetry in the F4 unit, resulting in two of the 19 F sites at the F4 unit being equivalent, while this symmetry is no longer present in mode III, where all four 19 F sites at the F4 unit are inequivalent.…”

Section: On the Basis Of The Observations From 2d 1 H-1 H Dq-sq And 1mentioning

confidence: 99%

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

et al. 2019

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Recent demonstrations of inverted thermal activation of charge mobility in polymer field-effect transistors have excited the interest in transport regimes not limited by thermal barriers. However, rationalization of the limiting factors to access such regimes is still lacking. An improved understanding in this area is critical for development of new materials, establishing processing guidelines, and broadening of the range of applications. Here we show that precise processing of a diketopyrrolopyrrole-tetrafluorobenzene-based electron transporting copolymer results in single crystal-like and voltage-independent mobility with vanishing activation energy above 280 K. Key factors are uniaxial chain alignment and thermal annealing at temperatures within the melting endotherm of films. Experimental and computational evidences converge toward a picture of electrons being delocalized within crystalline domains of increased size. Residual energy barriers introduced by disordered regions are bypassed in the direction of molecular alignment by a more efficient interconnection of the ordered domains following the annealing process.

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“…Compared with inorganic semiconducting single crystals, organic semiconducting single crystals (OSSCs) are composed of organic molecules that can be synthesized through molecular design to have tunable functions and hold the best promise of combining light weight, low cost, processability, and performance for large‐area device applications . Over the past decades, great advancements in OSSCs have been achieved, such as the modulation of crystal functions and habits, the improvement of crystal quality, the optimization of device configuration and interfacial contact, and a deep understanding of the fundamental and novel physics of organic semiconductors . For instance, Pope et al gave the first demonstration of electroluminescence in organic semiconductors, which were based on anthracene crystals, in 1963 .…”

Section: Introductionmentioning

confidence: 99%

Organic Semiconductor Single Crystals for Electronics and Photonics

2018

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Organic semiconducting single crystals (OSSCs) are ideal candidates for the construction of high-performance optoelectronic devices/circuits and a great platform for fundamental research due to their long-range order, absence of grain boundaries, and extremely low defect density. Impressive improvements have recently been made in organic optoelectronics: the charge-carrier mobility is now over 10 cm V s and the fluorescence efficiency reaches 90% for many OSSCs. Moreover, high mobility and strong emission can be integrated into a single OSSC, for example, showing a mobility of up to 34 cm V s and a photoluminescence yield of 41.2%. These achievements are attributed to the rational design and synthesis of organic semiconductors as well as improvements in preparation technology for crystals, which accelerate the application of OSSCs in devices and circuits, such as organic field-effect transistors, organic photodetectors, organic photovoltaics, organic light-emitting diodes, organic light-emitting transistors, and even electrically pumped organic lasers. In this context, an overview of these fantastic advancements in terms of the fundamental insights into developing high-performance organic semiconductors, efficient strategies for yielding desirable high-quality OSSCs, and their applications in optoelectronic devices and circuits is presented. Finally, an overview of the development of OSSCs along with current challenges and future research directions is provided.

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Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps

Abstract: CitationMei Y, Diemer PJ, Niazi MR, Hallani RK, Jarolimek K, et al. (2017) Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps.

Cited by 82 publications

References 99 publications

Charge‐Transport Properties of F₆TNAP‐Based Charge‐Transfer Cocrystals

Charge‐Transport Properties of F₆TNAP‐Based Charge‐Transfer Cocrystals

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

Organic Semiconductor Single Crystals for Electronics and Photonics

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Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps

Abstract: CitationMei Y, Diemer PJ, Niazi MR, Hallani RK, Jarolimek K, et al. (2017) Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps.

Cited by 82 publications

References 99 publications

Charge‐Transport Properties of F6TNAP‐Based Charge‐Transfer Cocrystals

Charge‐Transport Properties of F6TNAP‐Based Charge‐Transfer Cocrystals

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

Organic Semiconductor Single Crystals for Electronics and Photonics

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Product

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Charge‐Transport Properties of F₆TNAP‐Based Charge‐Transfer Cocrystals

Charge‐Transport Properties of F₆TNAP‐Based Charge‐Transfer Cocrystals