Experimental and Numerical Investigation of Contact Doping Effects in Dinaphthothienothiphene Thin‐Film Transistors

Abstract

Contact doping effects in p-channel dinaphthothienothiphene (DNTT) thin-film transistors with a bottomgate, top-contact configuration were investigated with both experimental and numerical approach. Characteristic variation in transistor parameters such as the gate threshold voltage and the field-effect mobility for devices with various channel lengths was suppressed by the contact doping with tetrafluorotetracyanoquinodimethane (F 4 TCNQ) as an acceptor dopant. The gate-voltage dependence of contact resistance and channel resistance was also evaluated separately to examine the contact doping effect in detail. In addition, device simulation considering a Schottky barrier at a metal/semiconductor interface successfully reproduced the experimental current-voltage characteristics by using a hole concentration of the active DNTT layer in the order of 10 17 cm −3 , which was estimated by capacitancevoltage measurement for a metal/insulator/semiconductor capacitor structure. This study suggests the importance of establishing both the carrier doping and carrier concentration measurements toward realizing practical applications of organic transistors. C⃝

Double Beneficial Role of Fluorinated Fullerene Dopants on Organic Thin-Film Transistors: Structural Stability and Improved Performance

“…In general, a critical aspect affecting the long-term stability of devices is the tendency of OSC films to dewet from SiO 2 . , In a previous study, we showed that C8-BTBT-C8 thin films suffer from a strong dewetting with time provoking notable degradation of the fabricated OFETs Figure a,d shows the topographic images of the as-grown BTBT-C8 film and the same sample measured after two years, respectively.…”

“…2,4 Besides, interfacial engineering may also reduce degradation with time due to film dewetting, a phenomenon strongly affecting the long-term stability of devices based on BTBT and related organic semiconductors. 36,37,38,39 Despite the importance of contact doping, very few studies have focused on specific properties of the dopant/OSC interface. Fundamental questions remain about how the physicochemical properties of the OSC surface influence the dopant/OSC interface characteristics and thereby the injection properties.…”

“…Along with the different strategies developed to improve device properties, there have been numerous advances in the synthesis of high-mobility OSCs as it is the case of the benzothieno­[3,2- b ]­[1]­benzothiophene (BTBT) derivatives, − affording OFETs with field-effect mobilities higher than 1.0 cm 2 /V s and using diverse fabrication processes. − Their low-lying highest occupied molecular orbital (HOMO) energy level ( E HOMO ) has allowed air-stable electrical performance, and alkyl side chain engineering has been widely applied to improve the materials’ solubility for solution processability . With the synthesis of OSCs with superior intrinsic charge transport properties and deep low-lying HOMO energy level ( E HOMO ≈ 5.4–5.8), ,, ensuring efficient charge carrier injection by tailoring the electrode/semiconductor interface has become a stringent need. , Besides, interfacial engineering may also reduce degradation with time because of film dewetting, a phenomenon strongly affecting the long-term stability of devices based on BTBT and related OSCs. − …”