Stability-improved organic n-channel thin-film transistors with nm-thin hydrophobic polymer-coated high-k dielectrics

Lee

et al. 2013

Adv Funct Materials

Self Cite

Small molecule pentacene layer has been a representative among many organic thin‐film transistor (OTFT) channels with decent p‐type mobilities, but it is certainly light‐sensitive due to its relatively small highest occupied molecular orbital‐lowest unoccupied molecular orbital (HOMO‐LUMO) gap (1.85 eV). Although a few other small molecule‐based layers have been reported later, their photo‐stabilities or related device applications have hardly been addressed. Here, a new photostable organic layer is reported, heptazole (C26H16N2), which has almost the same HOMO level as that of pentacene but with a higher HOMO‐LUMO gap (≈2.95 eV). This heptazole OTFT displays a decent mobility comparable to that of conventional amorphous Si TFTs, showing good photostability unlike pentacene OTFTs. An image pixel driving the photostable heptazole OTFT connected to a pentacene/Al Schottky photodiode is demonstrated. This heptazole OTFT also conveniently forms a logic inverter coupled with a pentacene OTFT, sharing Au for source/drain.

Section: Methodsmentioning

confidence: 99%

Photo‐Stable Organic Thin‐Film Transistor Utilizing a New Indolocarbazole Derivative for Image Pixel and Logic Applications

Lee

et al. 2013

Adv Funct Materials

Self Cite

“…Park et al [95] have shown that by using a bilayer structure of CYTOP/Al 2 O 3 the threshold voltage shift can be minimized. They fabricated and tested an n-channel OTFT based on N ,N -ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13).…”

Section: High-k/low-k Bilayer-based Otftsmentioning

confidence: 99%

Hybrid bilayer gate dielectric-based organic thin film transistors

Teja

Gupta

2019

Bull Mater Sci

Organic thin film transistors (OTFTs) are key building blocks for flexible, low cost electronics systems. They provide a viable alternative for silicon-based electronics with added advantages of low cost and flexibility. However, few issues like high-operating voltage, low-switching speed, high-leakage current and reliability are still a challenge. The overall performance of an OTFT depends on organic semiconductors and gate dielectric interface. In this paper, we review the current status and trends in the choice of dielectric layer for OTFTs. As a starting point, the performance parameters of an OTFT and their dependence on the dielectric layer are briefly discussed. A variety of dielectric materials which includes high-k inorganic, organic, surface coated inorganics and nanocomposites are also presented. The advantages and drawbacks of each of these materials are discussed in detail. We reviewed the latest developments in the dielectric materials especially, self-assembled monolayers (SAMs), hybrid bilayers and nanocomposites. SAM-based OTFTs offer several advantages but shift in the threshold voltage remains a concern. Nanocomposites are a latest addition to the dielectric materials, which offer advantages like solution processing and improved dielectric constant but have a rough surface. A hybrid bilayer that incorporates the inorganic dielectric as a base layer and a thin polymer layer over it to improve the surface properties offers several desirable characteristics over the other choices. Hence, we propose that hybrid bilayer gate dielectrics shall play a pivotal role in improving the OTFT performance.

“…To further improve the turn-on characteristics, there has been a focus on thin and high-κ dielectric layers to increase the gate capacitance, leading to a lower subthreshold swing. [16][17][18][19][20][21] In this study, we focus on the subthreshold regime from a microscopic perspective, especially its relation to the trap DOS. Single-crystal OFET measurements with extremely low subthreshold swing are presented, and the theoretical description of the subthreshold current to extract the trap DOS is summarized.…”

Section: Introductionmentioning

confidence: 99%

Approaching the Trap-Free Limit in Organic Single-Crystal Field-Effect Transistors

2014

We present measurements of rubrene single crystal field-effect transistors with textbooklike transfer characteristics, as one would expect for intrinsically trap-free semiconductor devices. Particularly, the high purity of the crystals and the defect-free interface to the gate dielectric are reflected in an unprecedentedly low subthreshold swing of 65 mV/decade, remarkably close to the fundamental limit of 58.5 mV/decade. From these measurements we quantify the residual density of traps by a detailed analysis of the subthreshold regime, including a full numerical simulation. An exceedingly low trap density of D bulk = 1 × 10 13 cm −3 eV −1 at an energy of ∼ 0.62 eV is found. This result corresponds to one trap per eV in 10 8 rubrene molecules. The equivalent density of traps located at the interface (Dit = 3 × 10 9 cm −2 eV −1 ) is as low as in the best crystalline SiO2/Si field-effect transistors. These results highlight the benefit of having van der Waals bonded semiconducting crystals without electronically active states due to broken bonds at the surface.