Roles of interfaces in the ideality of organic field-effect transistors

Controlling the interfacial properties between the electrode and active layer in organic field‐effect transistors (OFETs) can significantly affect their contact properties, resulting in improvements in device performance. However, it is difficult to apply to top‐contact‐structured OFETs (one of the most useful device structures) because of serious damage to the organic active layer by exposing solvent. Here, a spontaneously controlled approach is explored for optimizing the interface between the top‐contacted source/drain electrode and the polymer active layer to improve the contact resistance (RC). To achieve this goal, a small amount of interface‐functionalizing species is blended with the p‐type polymer semiconductor and functionalized at the interface region at once through a thermal process. The RC values dramatically decrease after introduction of the interfacial functionalization to 15.9 kΩ cm, compared to the 113.4 kΩ cm for the pristine case. In addition, the average field‐effect mobilities of the OFET devices increase more than three times, to a maximum value of 0.25 cm2 V−1 s−1 compared to the pristine case (0.041 cm2 V−1 s−1), and the threshold voltages also converge to zero. This study overcomes all the shortcomings observed in the existing results related to controlling the interface of top‐contact OFETs by solving the discomfort of the interface optimization process.

Section: Introductionmentioning

confidence: 99%

Tuning Interfacial Properties by Spontaneously Generated Organic Interlayers in Top‐Contact‐Structured Organic Transistors

Choi

Seo

et al. 2020

“…[ 20 ] In this respect, unearthing the originations of double‐slope behaviors and developing viable methods to eliminate their adverse effects are much essential. [ 24–27 ]…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies have shown that, in addition to the contact resistance, the minority injection also plays a crucial role in the resulting double‐slope behaviors. [ 22,25–29 ] For p‐type OFETs fabricated with narrow‐bandgap polymers and small molecules, recent researches have provided evidence that the observed double‐slope behaviors could also originate from undesirable electron (the minority charge carriers in p‐type OFETs) injection. [ 30–32 ] Due to the narrow bandgap of the active organic semiconductors (OSCs), electrons could be readily injected from the drain electrode when a positive gate bias is applied under device off‐state mode.…”

Section: Introductionmentioning

confidence: 99%

“…To avoid the detrimental effect of electron injection on the ideality and electrical stability of p‐type narrow‐bandgap OSC‐based OFETs, several strategies have been developed. [ 27 ] These strategies mainly fall into two categories based on their function mechanisms. One viable strategy is blocking the electron trapping process to overwhelm the detrimental effect of electron injection.…”

Section: Introductionmentioning

confidence: 99%

“…[5][6][7][8][9][10][11][12] Therefore, proof-of-concept demonstrations based on OFETs, including flat panel displays, radiofrequency identification tags, active-matrix imagers, conformable To avoid the detrimental effect of electron injection on the ideality and electrical stability of p-type narrow-bandgap OSCbased OFETs, several strategies have been developed. [27] These strategies mainly fall into two categories based on their function mechanisms. One viable strategy is blocking the electron trapping process to overwhelm the detrimental effect of electron injection.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Improving Ideality of P‐Type Organic Field‐Effect Transistors via Preventing Undesired Minority Carrier Injection

Jia

Pan

et al. 2021

Self Cite

Electron injection plays a crucial role in arousing the double‐slope characteristics for p‐type organic field‐effect transistors (OFETs) with narrow‐bandgap organic semiconductors (OSCs). This issue will not only result in the misrepresentation of OFET performance but also may cause device instability, hence impeding their further development in real‐world applications. A facile and highly efficient approach is developed to circumvent this issue by implementing modification on the electrode/organic semiconductor interface. An ultrathin layer of wide‐bandgap OSC with suitable energy levels is introduced to block the undesirable electron injection. By this means, typical double‐slope behaviors and bias stress stability in the p‐type OFETs can be significantly improved. Using 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl) anthradithiophene‐based OFETs the double‐slope behaviors of as‐fabricated devices are effectively converted to near‐ideal behaviors after modification, leading to a dramatic improvement of average reliability from 65.11% to 91.76%. Furthermore, the positive drift of transfer curves under prolonged bias stress is also successfully suppressed. This strategy demonstrates good universality and can provide a new guideline for the fabrication of OFETs with ideal behaviors.

Buried‐Contact Organic Field‐Effect Transistor: The Way of Alleviating Drawbacks from Interfacial Charge Transfer

Hwang,

Seo,

Tsogbayar

et al. 2024

Facile charge transfer between source/drain (S/D) electrodes and organic semiconductor (OSC) channel is crucial for high‐mobility organic field‐effect transistors (OFETs). Herein, a novel OFET geometry is developed by modifying a top‐contact bottom‐gate device structure, termed a buried‐contact OFET, enabling close proximity between the S/D‐OSC interface and conducting channel, consequently decreasing the access contact resistance (RC,acc) and overall contact resistance (RC). Conventional post‐thermal annealing is combined with a burying pressure (pressure‐thermal annealing (PTA)). The synergistic effect of thermal and pressure annealings leads to the softened OSC layer enabling metal electrodes to bury inward by applied pressure. This process induces structural transitions from a top‐contact to buried‐contact configuration, as verified by atomic force microscopy and finite element simulations. Transfer line method and 4‐probe measurements revealed that PTA reduces the contact by 1/3 (65 kΩ cm) and the source‐to‐drain voltage waste due to charge injection from 52% to 31%. Consequently, the field‐effect mobility is four times higher than that of a conventional thermally annealed top‐contact OFET. The density of deep traps (Ntr) is mainly distributed in the OSC bulk responsible for charge injection. Remarkably, the Ntr decreased 30‐fold using PTA, resulting in a shallow sub‐threshold region and a threshold voltage close to zero.