Vertical Phase Separation Structure for High‐Performance Organic Thin‐Film Transistors: Mechanism, Optimization Strategy, and Large‐Area Fabrication toward Flexible and Stretchable Electronics

Abstract

Organic thin-film transistors (OTFTs) exhibit great potential applications in flexible logic circuits, sensors, nonvolatile memory, etc. The vertical phase separation (VPS) structure, deriving from the blends of small molecules and polymers, can produce a high-quality crystalline semiconducting layer and an intrinsic and trap-free semiconductor/insulator interface. OTFTs with a VPS structure provide a promising route to accelerate their commercialization due to these desirable features including excellent device performance, good uniformity and reproducibility, environmental and mechanical stability, lowcost and large-area fabrication. Additionally, VPS OTFTs also exhibit a good balance between electronical properties and stretchability for intrinsic stretchable OTFTs. Herein, a comprehensive review is given on VPS structure for flexible and stretchable OTFTs. First, the evolution history of VPS structures and its formation mechanism are summarized. Based on the understanding of the VPS structure, the optimization strategies of VPS structures for highperformance OTFTs are presented. Subsequently, the large-area fabrication techniques of VPS structures, as well as the potential applications in flexible and stretchable OTFTs, are discussed. Finally, conclusions and outlook are provided for the further development of VPS structure in OTFTs. This review would promote the understanding and development of VPS structures in OTFTs, accelerating its applications in flexible and stretchable electronics.

Physical Mechanism of the Mechanical Bending of High-Performance Organic TFTs and the Effect of Atmospheric Factors

“…A 25 nm active layer of an organic semiconductor (OSC) (TruFlex OSC) was fabricated by spin-coating the small molecule (TMTES-pentacene) with a polymer binder blend from a solvent solution. Subsequently, annealing at 150 °C for 1 min was used for dry and vertical separation. , This blend of OSCs produced a film with a highly crystallized channel that showed good uniformity over the substrate. By exploiting the difference in the hydrophobicity of different components, phase separation between a polymer binder and small molecules was achieved, where small molecules remained on top. , …”

“…Subsequently, annealing at 150 °C for 1 min was used for dry and vertical separation. , This blend of OSCs produced a film with a highly crystallized channel that showed good uniformity over the substrate. By exploiting the difference in the hydrophobicity of different components, phase separation between a polymer binder and small molecules was achieved, where small molecules remained on top. , …”

“…By exploiting the difference in the hydrophobicity of different components, phase separation between a polymer binder and small molecules was achieved, where small molecules remained on top. 24,25 A small-molecule layer with intrinsic high mobility and the main channel current will flow at the interface between the OSC layer and the 110 nm low-k polar-free TruFlex OGI layer. 26 A 300 nm crosslinked organic polymer (TruFlex SRL) was deposited on the OGI by spin-coating and formed the sputter-resistant layer (SRL).…”

Microstructural Control of Soluble Acene Crystals for Field-Effect Transistor Gas Sensors

“…Because soluble acene has a low film-forming capability, polymer binders are typically added to prepare soluble acene solutions, and spin-casting, dip-coating, inkjet printing, and bar coating are applied to fabricate soluble acene/polymer blend films [ 17 , 39 , 43 , 44 , 45 ]. In addition to the insulating binder polymers, poly(triaryl amine) (PTAA) with the highest occupied molecular orbital level similar to that of soluble acene is used as the counterpart polymer in the preparation of the blend solution [ 6 , 64 ].…”

“…Here, inducing vertical phase separation in soluble acene/polymer blends is also necessary for fabricating FETs. Readers can read recent review papers focusing on obtaining high field-effect mobility in FETs based on soluble acene/polymer blends [ 17 , 18 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. Instead of introducing strategies for vertical phase separation, this review focuses on introducing key concepts in the microstructural control of soluble acene/polymer blends for high-performance gas sensors.…”