Organic Field Effect Transistors

[74] Stefanucci G, van Leeuwen R. Nonequilibrium Many-Body Theory of Quantum Systems: A Modern Introduction, Volume 54. Cambridge

*Integrated Circuits/Microchips*

[82] Szabo A, Koester SJ, Luisier M. Ab-initio simulation of van der Waals MoTe2-SnS2 heterotunneling FETs for low-power electronics. IEEE Electron Device Letters. 2015;**36**(5):514-516

Balakrishnan V, Klimeck G, Koh CK. Distributed non-equilibrium Green's function algorithms for the simulation

scattering. Journal of Applied Physics.

[84] Luisier M, Klimeck G. Atomistic full-band simulations of silicon nanowire transistors: Effects of electron-phonon scattering. Physical Review B: Condensed Matter and Materials Physics. 2009;**80**(15):155430

[85] Luisier M, Klimeck G. Simulation of nanowire tunneling transistors: From the Wentzel-Kramers-Brillouin approximation to full-band phononassisted tunneling. Journal of Applied

[86] Fonseca JE, Kubis T, Povolotskyi M, Novakovic B, Ajoy A, Hegde G, et al. Efficient and realistic device modeling from atomic detail to the nanoscale. Journal of Computational Electronics.

Physics. 2010;**107**(8):84507

[87] Chen FW, Ilatikhameneh H, Ameen TA, Klimeck G, Rahman R. Thickness engineered tunnel field-effect transistors based on phosphorene. IEEE Electron Device Letters. 2016;**3106**(3):

2013;**12**(4):592-600

130-133

of nanoelectronic devices with

[83] Cauley S, Luisier M,

2011;**110**(4):043713

[75] Haug H, Jauho A-P, Cardona M. Quantum kinetics in transport and optics of semiconductors, Volume 2.

[76] Marzari N, Mostofi AA, Yates JR, Souza I, Vanderbilt D. Maximally localized wannier functions: Theory and

[77] Cao J, Logoteta D, Ozkaya S, Biel B, Cresti A, Pala M, et al. A computational

International Electron Devices Meeting.

[78] Cao J, Logoteta D, Ozkaya S, Biel B, Cresti A, Pala MG, et al. Operation and

[79] Cao J, Cresti A, Esseni D, Pala M. Quantum simulation of a heterojunction

[80] Cao J, Park J, Triozon F, Pala MG, Cresti A. Simulation of 2d materialbased tunnel field-effect transistors: Planar vs. vertical architectures; 2018. p. 4. Available from: https://www. openscience.fr/IMG/pdf/iste\_compona

[81] Szabo A, Rhyner R, Luisier M. Ab-initio simulations of MoS2 transistors: From mobility calculation to device performance evaluation. In: Technical Digest - International Electron Devices Meeting, IEDM, Volume 2015.

IEEE; 2015. pp. 30.4.1-30.4.4

vertical tunnel FET based on 2D transition metal dichalcogenides. Solid-

State Electronics. 2016;**116**:1-7

no18v1n

**62**

applications. Reviews of Modern

study of van der Waals tunnel transistors: Fundamental aspects and

design challenges. In: IEDM,

design of van der Waals tunnel transistors: A 3-D quantum transport study. IEEE Transactions on Electron Devices. 2016;**63**(11):4388-4394

IEEE; 2015. pp. 313-316

Physics. 2012;**84**(4):1419

University Press; 2013

Springer; 2008

**65**

**Chapter 4**

**Abstract**

**1. Introduction**

Crystal Polymorph Control for

Organic molecules are assembled together by weak non-covalent intermolecular interactions in solid state. Multiple crystalline packing states (crystal polymorphism) have commonly existed in the active layer for organic field-effect transistors (OFETs). Different polymorphs, even with the slightest changes in their molecular packing, can differ the charge transport mobility by orders of magnitude. Therefore, accessing new polymorphs can serve as a novel design strategy for attaining high device performance. Here, we review the state of the art in this emerging field of crystal polymorph control. We firstly introduce the role of polymorphism and the methods of polymorph control in organic semiconductors. Then we review the latest studies on the performance of polymorphs in OFET devices. Finally, we discuss the advantages and challenges for polymorphism as a platform for the study of the relationship between molecular packing and charge transport.

**Keywords:** organic field-effect transistors, organic semiconductors, polymorphism,

An organic field-effect transistor (OFET) is a transistor using an organic semiconducting thin film as the active layer in its channel [1, 2]. Charge carriers are transported in the OFET active layer under the electric field. Through the design of new materials and the improvement of fabrication processes, many impressive developments in the field of OFETs have been achieved [3–6]. It has long been realized that the morphology of the active layer has a crucial impact on its charge transport properties. Tremendous efforts have been devoted to fabricate highly ordered crystalline films to achieve high device performance, including introduction of self-assembled monolayers [7–9], annealing [10, 11], off-center spin coating [4, 12, 13], and solution shearing [14, 15]. However, the lack of knowledge on the intrinsic properties of organic semiconductors remains the barrier for high-perfor-

Polymorphism of organic semiconductors has recently received much attention in the field of OFETs [16–18]. Different polymorphic crystals have the same molecular structure but a different molecular arrangement, which can be used as an ideal platform to correlate charge transport with respect to molecular arrangement. Through investigating OFETs with different polymorphs, the relationship between molecular packing and charge transport can be obtained. Recently, some ultra-high-mobility

High-Performance Organic

Field-Effect Transistors

*Zhi-Ping Fan and Hao-Li Zhang*

structure-property relationship, carrier mobility

mance materials being efficiently developed.
