Remarkably low flicker noise in solution-processed organic single crystal transistors

Abstract

Low-frequency noise generated by a fluctuation of current is a key issue for integrating electronic elements into a high-density circuit. Investigation of the noise in organic field-effect transistors is now sharing the spotlight with development of printed integrated circuits. The recent improvement of field-effect mobility (up to 15 cm 2 V −1 s −1 ) has allowed for organic integrated circuits with a relatively high-speed operation (~50 kHz). Therefore, an in-depth understanding of the noise feature will be indispensable to further improve the circuit stability and durability. Here we performed noise measurements in solution-processed organic single crystal transistors, and discovered that a low trap density-of-states due to the absence of structural disorder in combination with coherent band-like transport gives rise to an unprecedentedly low flicker noise. The excellent noise property in organic single crystals will allow their potential to be fully exploited for high-speed communication and sensing applications.

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

“…Nevertheless, trustable mobility values of polycrystalline thin films of didecyl‐DNTT 9 and didecyl‐DNBDT‐NW 13 , measured by the van der Pauw method, reach 6.2 and 6.5 cm 2 V −1 s −1 . Such mobility values are only inferior by a factor 2–3 to those obtained in single crystals, indicating that grain boundaries are not too limiting, at room temperature, for well‐fabricated thin films . However, this conclusion might not be general and not hold true at low temperature .…”

“…With Cytop dielectric layer, a charge carrier mobility of one order of magnitude higher was found and a trap DOS of two orders of magnitude lower . Very recently, noise spectroscopy has been demonstrated to be a powerful tool to extract the trap DOS in organic semiconductors by Watanabe et al for C8‐DNBDT‐NW 13 exhibiting a low energy‐independent trap DOS of 8.3 × 10 18 cm −3 eV −1 . Finally, the rate of charge carrier hopping between defects and escape of the charge carrier from a defect and into the band has been theoretically evaluated by McMahon and Troisi.…”

“…Not surprisingly, contact resistance has received considerable attention and several groups have worked on the modification of electrode surfaces, with SAM and dopants to understand and to improve charge injection. For best performing molecular semiconductors, such as dioctyl‐DNBDT‐NW 13 , a thin layer of about 1 nm of F4‐TCNQ is often used to improve charge injection . Metal oxides, such as MoO x have also been used as insertion layer between gold and BTBT 8 (various side chains) .…”

“…Takeya et al have developed and optimized the edge‐casting method to produce solution‐processed single‐crystals of few molecular layers of best performing herringbone materials presenting mobility values up to 15 cm 2 V −1 s −1 and the lowest reported noise in organic materials for C8‐DNBDT‐NW 13 . These results will be described more thoroughly in Section 2.5.2 . The group of Batlogg has highlighted the beneficial effect of Cytop, a highly water repellent fluoropolymer, eliminating the bias stress effect and leading to the systematic production of molecular single‐crystal devices of really high electrical quality presenting textbook‐like transfer characteristics: near zero onset, very steep subthreshold swing, negligible current hysteresis.…”

“…Mobility per se contains only limited information on charge transport and is one over several other electrical parameters of OFETs. For example, additional and valuable information on trap and release processes of charges can be extracted from the noise in electrical signals . This paper addresses the community of organic electronics to share with it a critical analysis of the best performing molecular semiconductors and of the inherent charge transport physics that takes place in them.…”