Title: Inkjet-printed rectifying metal-insulator-semiconductor (MIS) diodes for flexible electronic applications
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WF)) adjacent to the semiconductor. Figure 1. (b) shows a scheme for Schottky diode along with its corresponding energy band diagram at different biasing conditions. The contrasting metals or conducting polymers which can be considered are e.g. silver (bulk WF = 4.26 to 4.74 eV), copper (bulk WF = 4.53 to 5.10 eV), aluminium (bulk WF = 4.06 to 4.26 eV), poly (3,4ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT:PSS, WF = 5.1 eV), etc. When “Inkjet printing” as a deposition technology is considered, due to the sophisticated ink formulation (eg. nano-particles synthesis and its stable dispersion) and tedious post treatment procedures (eg. IPL sintering) [4], fabrication of these devices remains challenging.
(a)
(b) Figure 1. (a) Energy band diagram (reworked [7]) and (b) Scheme for Schottky diode architecture (Cross sectional view) Recently, it was reported that there are probably also further categories of diodes existing which can contain an additional insulating barrier layer as shown in Figure 2. [1, 7] These are diodes based on interfacial barrier layers. [1, 7, 8, 9, 10] In the inorganic metal-insulatorsemiconductor (MIS) devices where the conventional insulating silicon dioxide (SiO2) thickness is below 7 nm, the charge carriers can tunnel through the insulating barrier. [11] In MIS diodes, this causes a reduction in the reverse saturation current and an increase in the barrier height as shown in Figure 2. (a). [12] In principle a thick insulating layer with 50-200 nm will block the
carrier flow. It is expected that the diode behave as a capacitor. [7] However, if the insulating layer is leaky due to a non-homogeneous thickness or due to the penetration of the semiconductor through pinholes can give rise to a voltage controlled leakage and to corresponding asymmetric current vs. voltage curves.
(a)
(b) Figure 2. ( a) Energy band diagram (reworked [7]) and (b) Scheme for MIS diode architecture (Cross sectional view) Herein, we focused on printing the complete layer stack consisting of: (a) top and bottom printed conducting layers using a silver nanoparticle ink, (b) an insulating polymeric layer and (c) a polymeric semiconducting layer. The same behaviour of the MIS diode is shown using an insulating polymeric material poly(methylmethacrylate/methacrylic acid in ethtyl lactate) [MMAcoMAA] instead of growing oxide layer over the metal. MMAcoMAA has a leaky electrical insulating property which is intentionally expected. Additionally, we show that the metals having two different WF is not necessary to achieve rectifying current vs. voltage characteristics. EXPERIMENTAL: Printing was conducted based on the architecture described above in Figure 2. A nanoparticle silver ink namely SunTronic EMD 5603 from SunChemical, MMAcoMAA
poly(methylmethacrylate/methacrylic acid in ethtyl lactate) from MICROCHEM, the p-type organic semiconductor FS0027 from Flexink were used as the functional materials for manufacturing the MIS diodes on a heat stabilized flexible PEN (polyethylene naphthalate) Teonex Q65FA plastic su
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