Intrinsically ionic conductive cellulose nanopapers applied as all solid dielectrics for low voltage organic transistors

Abstract

Biodegradability, low-voltage operation, and flexibility are important trends for the future organic electronics. High-capacitance dielectrics are essential for low-voltage organic field-effect transistors. Here we report the application of environmental-friendly cellulose nanopapers as high-capacitance dielectrics with intrinsic ionic conductivity. Different with the previously reported liquid/electrolyte-gated dielectrics, cellulose nanopapers can be applied as all-solid dielectrics without any liquid or gel. Organic field-effect transistors fabricated with cellulose nanopaper dielectrics exhibit good transistor performances under operation voltage below 2 V, and no discernible drain current change is observed when the device is under bending with radius down to 1 mm. Interesting properties of the cellulose nanopapers, such as ionic conductivity, ultra-smooth surface (~0.59 nm), high transparency (above 80%) and flexibility make them excellent candidates as high-capacitance dielectrics for flexible, transparent and low-voltage electronics.

Fig. 1

Photograph and AFM characterization of ICCN. a Photograph of a highly transparent 40 μm-thick ICCN. b AFM image of a ICCN. c AFM line scan of a ICCN, shows ultra-smooth surface with RMS of ~0.59 nm

Fig. 2

Chemical structure, FTIR and XPS analysis of ICCNs. a The chemical structure of ICCNs pretreated with TEMPO. The FTIR spectra (b) and XPS spectrum (c) of a 40 μm-thick ICCN

Fig. 3

Frequency dependent effective capacitance of 40 μm thick ICCNs. a Frequency-dependent effective capacitance (C-f) of a 40 μm-thick ICCN measured in a metal/insulator/metal (Au/ICCN/Au) structure. b Schematic diagram demonstrates the formation of EDL in ICCNs under the action of electric field

Fig. 4

Schematic of transparent OFET based on ICCN. a Schematic illustration of the ICCN based OFETs with a bottom gate top contact architecture. b Optical transmittance of a 40 μm-thick ICCN and an ICCN/C8-BTBT composite film at different wavelengths

Fig. 5

Electrical characteristics of ICCNs based OFETs. a, b I_d–V_d curves and c transfer characteristics curves (I_d–V_g) of a p-channel C8-BTBT OFET. d, e I_d−V_d curves and f transfer characteristics curves (I_d−V_g) of a n-channel NTCDI-F15 OFET. g, h I_d−V_d curves and i transfer characteristics curves (I_d−V_g) of a PQT-12 OFET

Fig. 6

Bending tests on flexible OFETs. a Normalized maximum drain current at V_g of −6 V and V_d of −5 V (normalized to the initial drain current measured in the flat state) as a function of the bending radius. Error bars represent standard errors from five times independent tests of a device. b The picture depicts implementation of this bending test

Fig. 7

Organic complementary inverter on ICCN dielectrics. a Image of an organic complementary inverter and its simplified circuit diagram. b Output voltage and c gain as a function of the input voltage with supply voltage step between 2−5 V. The input voltage was swept from −2 to 4 V