Diffractive X-ray Waveguiding Reveals Orthogonal Crystalline Stratification in Conjugated Polymer Thin Films

Gann, Eliot,Caironi, Mario,Noh, Yong-Young,Kim, Yun-Hi,McNeill, Christopher R. American Chemical Society 2018 Macromolecules Vol.51 No.8

<P>The depth dependence of crystalline structure within thin films is critical for many technological applications but has been impossible to measure directly using common techniques. In this work, by monitoring diffraction peak intensity and location and utilizing the highly angle-dependent waveguiding effects of X-rays near grazing incidence, we quantitatively measure the thickness, roughness, and orientation of stratified crystalline layers within thin films of a high-performance semiconducting polymer. In particular, this diffractive X-ray waveguiding reveals a self-organized 5 nm thick crystalline surface layer with crystalline orientation orthogonal to the underlying 65 nm thick layer. While demonstrated for an organic semiconductor film, this approach is applicable to any thin film material system with stratified crystalline structure where orientation can influence important interfacial processes such as charge injection and field-effect transport.</P> [FIG OMISSION]</BR>

Control of Polymer Directional Alignment via Simple Off-center Spin-coating for High Performance Organic Field Effect Transistors

김남구,장수영,Giuseppina Pace,Mario Caironi,박원태,노용영,김동유 한국고분자학회 2015 한국고분자학회 학술대회 연구논문 초록집 Vol.2015 No.10

Toward Printed Integrated Circuits based on Unipolar or Ambipolar Polymer Semiconductors

Baeg, Kang‐,Jun,Caironi, Mario,Noh, Yong‐,Young WILEY‐VCH Verlag 2013 ADVANCED MATERIALS Vol.25 No.31

<P><B>Abstract</B></P><P>For at least the past ten years printed electronics has promised to revolutionize our daily life by making cost‐effective electronic circuits and sensors available through mass production techniques, for their ubiquitous applications in wearable components, rollable and conformable devices, and point‐of‐care applications. While passive components, such as conductors, resistors and capacitors, had already been fabricated by printing techniques at industrial scale, printing processes have been struggling to meet the requirements for mass‐produced electronics and optoelectronics applications despite their great potential. In the case of logic integrated circuits (ICs), which constitute the focus of this Progress Report, the main limitations have been represented by the need of suitable functional inks, mainly high‐mobility printable semiconductors and low sintering temperature conducting inks, and evoluted printing tools capable of higher resolution, registration and uniformity than needed in the conventional graphic arts printing sector.</P><P>Solution‐processable polymeric semiconductors are the best candidates to fulfill the requirements for printed logic ICs on flexible substrates, due to their superior processability, ease of tuning of their rheology parameters, and mechanical properties. One of the strongest limitations has been mainly represented by the low charge carrier mobility (<I>μ</I>) achievable with polymeric, organic field‐effect transistors (OFETs). However, recently unprecedented values of <I>μ</I> ∼ 10 cm<SUP>2</SUP>/Vs have been achieved with solution‐processed polymer based OFETs, a value competing with mobilities reported in organic single‐crystals and exceeding the performances enabled by amorphous silicon (a‐Si). Interestingly these values were achieved thanks to the design and synthesis of donor‐acceptor copolymers, showing limited degree of order when processed in thin films and therefore fostering further studies on the reason leading to such improved charge transport properties. Among this class of materials, various polymers can show well balanced electrons and holes mobility, therefore being indicated as ambipolar semiconductors, good environmental stability, and a small band‐gap, which simplifies the tuning of charge injection. This opened up the possibility of taking advantage of the superior performances offered by complementary “CMOS‐like” logic for the design of digital ICs, easing the scaling down of critical geometrical features, and achieving higher complexity from robust single gates (e.g., inverters) and test circuits (e.g., ring oscillators) to more complete circuits.</P><P>Here, we review the recent progress in the development of printed ICs based on polymeric semiconductors suitable for large‐volume micro‐ and nano‐electronics applications. Particular attention is paid to the strategies proposed in the literature to design and synthesize high mobility polymers and to develop suitable printing tools and techniques to allow for improved patterning capability required for the down‐scaling of devices in order to achieve the operation frequencies needed for applications, such as flexible radio‐frequency identification (RFID) tags, near‐field communication (NFC) devices, ambient electronics, and portable flexible displays.</P>

Charge Injection Engineering of Ambipolar Field-Effect Transistors for High-Performance Organic Complementary Circuits

Baeg, Kang-Jun,Kim, Juhwan,Khim, Dongyoon,Caironi, Mario,Kim, Dong-Yu,You, In-Kyu,Quinn, Jordan R.,Facchetti, Antonio,Noh, Yong-Young American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.8

<P>Ambipolar π-conjugated polymers may provide inexpensive large-area manufacturing of complementary integrated circuits (CICs) without requiring micro-patterning of the individual p- and n-channel semiconductors. However, current-generation ambipolar semiconductor-based CICs suffer from higher static power consumption, low operation frequencies, and degraded noise margins compared to complementary logics based on unipolar p- and n-channel organic field-effect transistors (OFETs). Here, we demonstrate a simple methodology to control charge injection and transport in ambipolar OFETs via engineering of the electrical contacts. Solution-processed caesium (Cs) salts, as electron-injection and hole-blocking layers at the interface between semiconductors and charge injection electrodes, significantly decrease the gold (Au) work function (∼4.1 eV) compared to that of a pristine Au electrode (∼4.7 eV). By controlling the electrode surface chemistry, excellent p-channel (hole mobility ∼0.1–0.6 cm<SUP>2</SUP>/(Vs)) and n-channel (electron mobility ∼0.1–0.3 cm<SUP>2</SUP>/(Vs)) OFET characteristics with the same semiconductor are demonstrated. Most importantly, in these OFETs the counterpart charge carrier currents are highly suppressed for depletion mode operation (<I>I</I><SUB>off</SUB> < 70 nA when <I>I</I><SUB>on</SUB> > 0.1–0.2 mA). Thus, high-performance, truly complementary inverters (high gain >50 and high noise margin >75% of ideal value) and ring oscillators (oscillation frequency ∼12 kHz) based on a solution-processed ambipolar polymer are demonstrated.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-8/am200705j/production/images/medium/am-2011-00705j_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am200705j'>ACS Electronic Supporting Info</A></P>

High-Performance Organic Field-Effect Transistors with Directionally Aligned Conjugated Polymer Film Deposited from Pre-Aggregated Solution

Kim, Nam-Koo,Jang, Soo-Young,Pace, Giuseppina,Caironi, Mario,Park, Won-Tae,Khim, Dongyoon,Kim, Juhwan,Kim, Dong-Yu,Noh, Yong-Young American Chemical Society 2015 Chemistry of materials Vol.27 No.24

<P>In this report, we investigate a formation mechanism for polymer chains aligned with various semiconductor polymers and a microstructure for directionally aligned film through systematic analysis that includes polarized UV–visible–near infrared (UV–vis–NIR) absorption spectroscopy, atomic force microscopy, polarized charge modulation microscopy (<I>p</I>-CMM), and incident X-ray diffraction (GIXD) measurements. Through this study, we make two important observations: first, the highly aligned organic polymer semiconductor films are achieved by off-center spin coating of the preaggregated conjugated polymer solution. Second, the directionally aligned conjugated polymer films exhibit a larger anisotropy on the top surface compared with bulk film, which allows effective mobility improvement in top-gate/bottom-contact field-effect transistors with high performance uniformity. Finally, we demonstrate high-mobility organic field-effect transistors (OFETs) (7.25 cm<SUP>2</SUP>/(V s)) with a mobility large anisotropy (37-fold) using poly[(<I>E</I>)-1,2-(3,3′-dioctadecyl-2,2′- dithienyl)ethylene-<I>alt</I>-dithieno-(3,2-b:2′,3′-d)thiophene] (P18) as the semiconductor layer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-24/acs.chemmater.5b03775/production/images/medium/cm-2015-03775f_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b03775'>ACS Electronic Supporting Info</A></P>

Biodegradable all-polymer field-effect transistors printed on Mater-Bi

Stucchi Elena,Maksimovic Ksenija,Bertolacci Laura,Viola Fabrizio Antonio,Athanassiou Athanassia,Caironi Mario 한국정보디스플레이학회 2021 Journal of information display Vol.22 No.4

The growing demand of disposable electronics raises serious concerns for the corresponding increase in the amount of electronic waste, with severe environmental impact. Organic and flexible electronics have been proposed long ago as a more sustainable and energy-efficient technological platform with respect to established ones. Yet, such technology is leading to a drastic increase of plastic waste if common approaches for flexible substrates are followed. In this scenario, biodegradable solutions can significantly limit the environmental impact, actively contributing to eliminate the waste streams (plastic or electronic) associated with disposal of devices. However, achieving suitably scalable processes to pattern mechanically robust organic electronics onto largely available biodegradable substrates is still an open challenge. In this work, all-organic and highly flexible fieldeffect transistors, inkjet printed onto the biodegradable and compostable commercial substrate Mater-Bi, are demonstrated. Because of the thermal instability of Mater-Bi, no annealing steps are applied, producing devices with limited carrier mobility, yet showing correct n-type behavior and robustness to bending and crumpling. The degradation behavior of the final system shows unaltered biodegradability level according to ISO 14851. These results represent a promising step toward sustainable flexible and large-area electronics, combining energy and materials efficient processes with largely available biodegradable substrates.

IUPAC-PSK40: N-Channel Organic Field-Effect Transistors and Structure-Property Relationship

Min Jae Sung,Alessandro Luzio,Won-Tae Park,Ran Kim,Eliot Gann,Francesco Maddalena,Giuseppina Pace,Yong Xu,Dario Natali,Carlo de Falco,Long Dang,Christopher R. McNeill,Mario Caironi,Yong-Young Noh,Yun- 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2