Transfer printing as a method for fabricating hybrid devices on flexible substrates

Abstract

Printing methods are becoming important in the fabrication of flexible electronics. A transfer printing method has been developed for the fabrication of organic thin-film transistors (OTFT), capacitors, resistors and inductors onto plastic substrates. The method relies primarily on differential adhesion for the transfer of a printable layer from a transfer substrate to a device substrate. A range of materials applications is illustrated, including metals, organic semiconductors, organic dielectrics, nanotube and nanowire mats, a patterned inorganic semiconductor and graphene. Transfer printing can be used to create complex structures including many disparate materials sequentially printed onto the flexible substrate, with no mixed processing steps performed on the device substrate. Specifically, the fabrication and performance of model OTFT devices consisting of a polyethylene terephthalate (PET) substrate, gold (Au) gate and source/drain electrodes, a poly(methyl methacrylate) (PMMA) dielectric layer and either a pentacene (Pn) or a poly(3-hexylthiophene) (P3HT) organic semiconductor layer will be presented. These transfer printed OTFTs on plastic outperform non-printed devices on a Si substrate with a SiO 2 dielectric layer (SiO 2 /Si). Transfer printed Pn OTFTs on a plastic substrate have exhibited mobilities of 0.237 cm 2 /Vs, compared to non-printed Pn OTFTs on a SiO 2 /Si substrate with mobilities of 0.1 cm 2 /Vs. Transfer printed P3HT TFTs on a plastic substrate have exhibited mobilites of 0.04 cm 2 /Vs, compared to non-printed P3HT TFTs on a SiO 2 /Si substrate with mobilities of 0.007 cm 2 /Vs.

Transfer Printing Techniques for Materials Assembly and Micro/Nanodevice Fabrication

“…Other schemes to enhance transfer use heat and pressure, as demonstrated in the printing of poly(3,4‐ethylenedioxythiophene) (PEDOT) onto pentacene 299. Similar ideas can be implemented to transfer all of the separate components of an organic thin film transistor (OTFT), including the metal, polymer, and organic semiconductor layers, occasionally with the assistance of intervening adhesive layers 300–302. Also, printed bi‐layers of poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and Au to N,N′‐di(naphthalene‐1‐yl)‐N,N′‐diphenylbenzidine (NPB) can form OLEDs 303.…”

Poly(3-hexylthiophene) thin-film transistors with variable polymer dielectrics for transfer-printed flexible electronics

“…The threshold voltage trends monotonically with the surface energy, indicating that the choice of dielectric materials can be used to tune the properties of the resulting OTFT device. The demonstration of transfer-printed OT-FTs with different substrate and dielectric materials as well as both small molecule 11,12,30,34 and polymeric organic semiconductor materials illustrates the broad applicability of the transfer printing process.…”

2D printing of graphene: a review

“…Elevated temperatures can facilitate the transfer process. As illustrated in figure 13, the stronger noncovalent adhesion between the graphene and the target substrate compared to the adhesion operating on the graphene and the transfer substrate is what makes the printing possible [69]. An examination of this adhesion mechanism is described in [70].…”