Photolithographic High‐Conductivity Transparent Conformal rGO/PEDOT:PSS Electrodes for Flexible Skin‐Like All Solution‐Processed Organic Transistors

Abstract

outstanding advantages of OFETs in intrinsic flexibility and even stretchability ensure the electronic devices seamlessly attach to the deforming objects, which will promote the development of emerging applications, for example, soft robotics, in-time medical monitoring, prostheses, conformal displays, and smartphones. [5][6][7][8][9] As one of the components of OFETs, the electrode determines the charge injection/ collection efficiency and affects charge transport, thereby affecting the fieldeffect performance. [10][11][12][13][14] Simultaneously, its mechanical properties, transparency, and patterning are also important factors influencing the mechanical flexibility and functionalization of OFETs. For example, excellent mechanical flexibility ensures mechanical robustness of electronic devices and the adherence capability of devices onto the natural skin or human organs, high transparency could expand the applications of OFETs in the next-generation "see-through" or "invisible" electronics, and electrode patterning is one of the key steps in devices miniaturization and integration. [15][16][17] Solution-processed conductive materials are of considerable interest for large-area, low-cost thin-film OFETs. Several solution-processed conductive materials, such as poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS), silver nanowires, carbon nanotubes, reduced graphene oxide (rGO), and polypyrrole, have been exploited as electrodes of OFETs. [18][19][20][21][22] Among them, rGO is considered to be the promising candidate electrode material because of its excellent properties, including high transparency, low cost, good chemical stability, and compatibility with organic semiconductors. [23,24] Currently, the patterned rGO as the electrode for OFET devices have been produced by inkjet printing, electron beam lithography, and photolithography techniques. [25][26][27] As far as we know, most of the currently reported rGO electrodes used in OFET devices were fabricated on rigid Si substrates. Only a few innovative studies were based on flexible PET substrates, which are incompatible with highly conformable skin-like electronics. [25,28] Additionally, rGO as the electrodes of OFETs have presented the low conductivity at 3.33-71 S cm −1 , originating from the lack of carbon Reduced graphene oxide (rGO) electrodes are known to exhibit high transparency, excellent chemical stability, low-cost solution processability, and good compatibility for use in solution-processed organic transistors, but they face fundamental challenges in conductivity and conformability for skin-like electronics. Here, by inserting a poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS) layer, the photolithographic conformal rGO/PEDOT:PSS electrodes with conductivity as high as 2000 S cm −1 can be achieved. Simultaneously, the rGO/PEDOT:PSS hybrid electrodes exhibit high precision down to 1 µm, high transparency of >90% over the visible spectra (400-700 nm), and imperceptible adherence onto damselfly wing without affecti...

Highly Strain‐Stable Intrinsically Stretchable Olfactory Sensors for Imperceptible Health Monitoring

“…It is worth noting that the semiconductor layer is deliberately exposed on the top of the device, so that the semiconductor layer can easily contact with the gas molecules for gas sensing, which is different from our previously reported stretchable transistors where the semiconductor was sandwiched between source/drain and gate electrodes. [ 42 , 43 , 44 ] In addition, the utilization of PEDOT:PSS&SWCNTs as an electrode material offers a notable advantage in terms of high‐precision patterning (down to 3 µm) through photolithography, surpassing conventional electrode materials such as carbon nanotube/metal nanowire networks, liquid metal, and doped elastomers. This characteristic lays a solid foundation for the development of highly integrated skin‐like gas sensor arrays in future applications.…”

Biomineral-Based Composite Materials in Regenerative Medicine

“…For an implant to be successful, the biominerals employed must exhibit biocompatibility and non-toxicity to the body’s surrounding cells [ 98 ]. While polymeric and metallic materials may provide the necessary spatial and mechanical support for cell attachment and proliferation, they typically lack biological activity and do not facilitate cell differentiation [ 99 ]. Conversely, biominerals can supply bioactive cations (e.g., Ca 2+ , Mg 2+ , and Si 4+ ) and anions (e.g., OH − and PO 4 3 − ), which are pivotal in the cell differentiation process within the body [ 100 , 101 ].…”

Recent advances in the construction and application of stretchable PEDOT smart electronic membranes

“…As shown in Fig. 17b-i, Wang et al 55 prepared all-solution treated OFETs by lithographing rGO electrodes onto PDMS substrates, and inserting PEDOT:PSS films into the rGO electrodes could effectively improve the conductivity of the hybrid electrodes (2000 S cm −1 ). The high conductivity of rGO/PEDOT:PSS enhances the modulation effect of the gate voltage on the current, and the mobility increases from 0.30 to 1.966 cm 2 V −1 s −1 .…”