Organic Single-Crystalline p–n Heterojunctions for High-Performance Ambipolar Field-Effect Transistors and Broadband Photodetectors

Abstract

Organic semiconducting single crystals are ideal building blocks for organic field-effect transistors (OFETs) and organic photodetectors (OPDs) because they can potentially exhibit the best charge transport and photoelectric properties in organic materials. Nevertheless, it is usual for single-crystal OFETs to be built from one kind of organic material in which the dominant transport is either electron or hole; such OFETs showing unipolar charge transport. Furthermore, single-crystal OPDs present high performance only in restricted regions because of the limited absorption of one-component single crystals. In an ideal situation, devices which comprise both electron and hole transporting single crystals with complementary absorptions, like single-crystalline p-n heterojunctions (SCHJs), can permit broadband photo-response and ambipolar charge transport. In this paper, a solution-processing crystallization strategy to prepare an SCHJ composed of C 60 and 6,13bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) was shown. These SCHJs demonstrated ambipolar charge transport characteristics in OFETs with a balanced performance of 2.9 cm 2 V −1 s −1 for electron mobility and 2.7 cm 2 V −1 s −1 for hole mobility. This demonstration is the first of single-crystal OFETs in which both electron and hole mobilities were over 2.5 cm 2 V −1 s −1 . OPDs fabricated upon as-prepared SCHJs exhibited highly-sensitive photo-conductive properties ranging from ultraviolet to visible and further to near-infrared regions as a result of complementary absorption between C 60 and TIPS-PEN; thereby attaining the photo-responsivities amongst the highest-reported values within the organic photodetectors. This work would provide valuable references for developing novel SCHJ systems to achieve significant progress in high-performance ambipolar OFETs and broadband OPDs. IntroductionRecently, continuous research attention has been drawn to organic field-effect transistors (OFETs) for lightweight and deformable electronic applications like photodetectors, 1 sensors, 2 displays, 3 and circuits. 4 Included in these, organic photodetectors (OPDs), which translate optical signals into electrical signals, occupy an essential position in optical interconnection techniques, light-wave communications,

Recent Advances in Ambipolar Transistors for Functional Applications

“…Transfer characteristics of OFETs on the basis of TIPS‐PEN/C 60 SCHJ operated under n‐channel f) and p‐channel g) regimes, respectively. Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…The orthogonal solvents based spin‐coating method is widely adopted to reduce the damage to the bottom layer after the sequential deposition . Up to now, among various bilayer ambipolar transistors based on small molecules, Zhao et al manufactured single‐crystal transistors with highest well‐balanced carrier mobilities of more than 2.5 cm 2 V −1 s −1 (2.9 cm 2 V −1 s −1 for electrons and 2.7 cm 2 V −1 s −1 for holes) by utilizing single‐crystalline p–n heterojunctions (SCHJs) comprising p‐type 6,13‐bis(triisopropylsilylethynyl)pentacene (TIPS‐PEN) and n‐type C 60 (Figure f,g), which stimulates more exploration of new SCHJ systems for high‐performance ambipolar transistors …”

Semiconductor/dielectric interface in organic field-effect transistors: charge transport, interfacial effects, and perspectives with 2D molecular crystals

“…In recent research, various techniques have been extensively used to achieve high-quality 2D organic crystalline films, such as floating-coffee-ring assembly [38], solution shearing [113], dip-coating [114,115], drop-casting [116], antisolvent-assisted spin coating [63] and solution epitaxy [43,117]. The superior interface qualities of the highly uniform 2DMCs with long-range molecular ordering can be promising materials to overcome the obstacles in traditional organic thin films, excluding the effects of extrinsic factors [5,41,118,119]. Therefore, the 2DMCs can provide great possibilities to directly explore the intrinsic nature of the charge carrier behaviours at the semiconductor/dielectric interface.…”

Fullerene Desymmetrization as a Means to Achieve Single‐Enantiomer Electron Acceptors with Maximized Chiroptical Responsiveness

“…They remain the most widely used electron acceptors in organic/hybrid photovoltaic devices (OPVs), [ 1–4 ] while also demonstrating excellent photo responsivity as broadband photodetectors. [ 5–10 ] Parent fullerene structures have extremely challenging solubility, which limits their processability and miscibility with host materials in bulk heterojunction OPVs; an issue which has been addressed through the production of more soluble derivatives using simple cycloaddition chemistry. Bis[60]PCBM (PCBM = phenyl‐C61‐butyric acid methyl ester) (dimethyl 4,4′‐[61,62‐diphenly,3′H,3″H‐dicyclopropa(C 60 I h )[5,6]fulleren‐1,9:X,Y‐diyl]dibutanoate) is one such derivative and one of the most utilized solubilized fullerenes, which is easy to synthesize, highly processable, and solar cells based on this material have high power conversion efficiencies.…”