Improved performance uniformity of inkjet printed n-channel organic field-effect transistors and complementary inverters Kang-Jun Baeg b,c , Dongyoon Khim b , Ju-Hwan Kim b , Minji Kang b , In-Kyu You c , Dong-Yu Kim b , Yong-Young Noh a,⇑ a Department of Chemical Engineering, Hanbat National University, 16-1 Dukmyung-dong, Yuseong-gu, Daejeon 305-719, Republic of Korea b Heeger Center for Advanced Materials, Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro (Oryong-dong), Buk-gu, Gwangju 500-712, Republic of Korea c Convergence Components and Materials Research Laboratory, Electronics and Telecommunications Research Institute (ETRI), 218 Gajeongno, Yuseong-gu, Daejeon 305-700, Republic of Korea article info Article history: Received 14 September 2010 Received in revised form 13 January 2011 Accepted 17 January 2011 Available online 1 February 2011 Keywords: Organic field-effect transistors Inkjet printing Conjugated molecule abstract In the present study, we demonstrate inkjet-printed n-type organic field-effect transistors (OFETs) and their complementary inverters with high performance uniformity, using soluble N,N 0 -bis(n-octyl)-(1,7&1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI8-CN 2 ). The device performance and uniformity were improved by ink-jet printing a PDI8-CN 2 solution onto a heated substrate (60 °C). The printed features, which were discontinuous crystalline films at RT, were uniform films when the substrate temperature was increased to 60 °C. Opti- mized n-channel PDI8-CN 2 FETs showed a high field-effect mobility of 0.05–0.06 cm 2 /Vs, a high on/off ratio of 10 6 , and a high uniformity that was within 10% with a bottom-gate/bot- tom-contact device configuration. Inkjet-printed organic complementary inverters were constructed by direct inkjet-printing of n-channel (PDI8-CN 2 ) and p-channel (6,13-bis(triiso- propyl-silylethynyl)-pentacene or poly(3-hexylthiophene)) organic semiconductors onto silicon dioxide gate dielectrics. The inkjet-printed organic complementary inverters exhib- ited a high voltage gain of more than 15 and small standard deviation of inverting voltage and gain of ±0.95 V and ±0.56, respectively, for measuring 12 samples from four difference batches. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Complementary metal–oxide–semiconductor (CMOS) inverters, which are composed of both p-type and n-type transistors, are fundamental logic circuits in current micro- processors and most advanced integrated circuits. The advantages of CMOS inverters include both higher noise immunity and lower static power consumption than n- type-only or p-type-only MOS inverters [1–3]. Currently, solution-processible organic field-effect transistors (OFETs) and complementary circuits are being developed to realize large-area flexible electronics, such as digital processors in radio-frequency identification (RFID) tags and driver cir- cuits in full color flexible displays, via cost-effective graphic art printing techniques [4–6]. To achieve these low-cost and high-speed organic complementary circuits, high perfor- mance n- and p-channel OFETs that have well-balanced charge carrier mobility must be realized by direct printing methods. Earlier studies that aimed to develop soluble con- jugated molecules as the active layer of OFETs were focused mainly on high-performance p-type organic semiconduc- tors because of their facile chemical synthesis [7–10]. These previous studies resulted in the development of state-of- the-art, soluble p-type organic small molecules and poly- mers that exhibit field-effect mobilities, l FET (1 cm 2 /Vs), comparable to those of amorphous silicon transistors [9,10]. In recent years, research has focused on the develop- ment of high-performance and air-stable n-type conjugated molecules [6,11]. 1566-1199/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.orgel.2011.01.016 ⇑ Corresponding author. E-mail address: yynoh@hanbat.ac.kr (Y.-Y. Noh). Organic Electronics 12 (2011) 634–640 Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel