The newly emerging field in organic electronics is to control the molecule−substrate interface properties at a two-dimensional (2D) limit via interfacial interactions, which paves the way for driving the molecular assembly for highly ordered 2D molecular crystalline films with precise molecular layers and large-area uniformity. Here, by exploiting molecule−substrate van der Waals (vdW) interactions, we demonstrate thermally induced self-assembly of 2D organic crystalline films exhibiting well-defined molecular layer number over a millimeter-sized area. The organic field-effect transistors (OFETs) with bilayer films show excellent electrical performance with a maximum mobility of 12.8 cm 2 V −1 s −1 . Moreover, we find that the monolayer films can act as interfacial molecular templates to construct heterojunctions with well-balanced ambipolar transport behaviors. The capability of thermally induced selfassembly of 2D molecular crystalline films with controllable molecular layers and scale-up coverage opens up a way for realizing complicated electronic applications, such as lateral heterojunctions and superlattices.
At present, the electrical performance of organic field-effect transistors (OFETs) has reached the level of commercial amorphous silicon. OFETs show considerable application potential in artificial intelligence, deep learning algorithms, and artificial skin sensors. The devices which can operate with high performance and low power consumption are needed for these applications. The recent energyrelated improvement to realize low-power consumption OFETs were reviewed, including minimizing operating voltage, reducing subthreshold swing, and decreasing contact resistance. In this review, we demonstrate breakthroughs in materials and methods to decrease power consumption, providing a promising avenue toward low-power consumption organic electronics. IntroductionFollowing the seminal paper from Tsumura, in which he demonstrated the first polythiophene-based field-effect transistor in 1986, organic field-effect transistors (OFETs) have received tremendous developments due to the intriguing properties of organic semiconductors, such as flexibility, stretchability, biocompatibility, solution processibility, and low cost [1][2][3][4]. To date, the field-effect mobility, which is the main character of an OFET device, has increased over 40 cm 2 V −1 s −1 . With the improvements in electric performance, the large-scale integration of OFETs have facilitated impressive application demonstrations, including organic light-emitting diode displays, radiofrequency identification tagging, and artificial skin [5][6][7][8][9][10][11][12]. To meet the future demand for product miniaturization and high properties, the number and density of transistors need to be increased, thus the heat energy caused by the power dissipation will lead to the degradation of organic materials and the life reduction of devices [13][14][15][16][17][18][19]. In addition, high power consumption limits the applications of most portable electronics which need an external battery [20][21][22][23]. All of these demands in applications require transistors to operate with extremely low-power consumption. However, power dissipation of most OFETs suffers from a high operating voltage typically a few tens of volts, which has a quadratic effect on dynamic power consumption [3,[24][25][26][27][28][29]. Furthermore, transistors sizes are also now approaching the point where quantum effects become appreciable, which can lead to an increased gate leakage current due to quantum tunneling and, in turn, an increased static power consumption.Achieving extremely energy-efficient OFETs is an essential prerequisite for commercial applications. After years of expansive development, significant advancements have been made in fabricating high quality dielectrics, thus reducing the operating voltage and leakage current. Furthermore, the subthreshold slope, which is negative correlation with switching efficiency, has witnessed a significant decrease driven by the process optimization and interface engineering [6,[30][31][32]. Additionally, the contact between semiconductors and electro...
Despite the great efforts to unveil the charge carrier behavior at the semiconductor/dielectric interface of organic field-effect transistors, an examination of the interfacial carrier distribution and the correlation with the charge transport in molecular crystalline semiconductors remains fundamental for understanding the nature of the microscopic carrier motion. Hence, an effective approach to accurately tune the carrier distribution with molecular-layer precision is essential. Here, we find that the carrier accumulation is strictly modulated in highly ordered, few-layer molecular crystalline semiconducting films by tuning the polaronic coupling between the charge carriers and dielectric. The admittance method reveals that the carriers distribute only within a monolayer with stronger localization on a high-κ dielectric and extend to a second layer with better delocalization on a low-κ dielectric. Furthermore, a unique dimensional transition in the charge transport at the dielectric interface is evidenced under a transistor architecture by temperature-dependent measurements. The presented microscopic nature of charge carriers with layer-defined precision in molecular crystalline films should provide an unprecedented opportunity in organic electronics in terms of interface engineering, quantum transport, and device physics.
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