Challenging Bendable Organic Single Crystal and Transistor Arrays with High Mobility and Durability toward Flexible Electronics

Abstract

materials have intrinsic advantages to meet these requirements, and they can adapt to various complex and extreme flexibility conditions to maintain performance without significant degradation. [7][8][9] However, organic semiconductor films used in flexible electronics are almost polycrystalline or amorphous, which severely limits the availability of high carrier mobility owing to the existence of a large number of grain boundaries, defects, and traps in the film. [9][10][11][12][13] Therefore, organic single crystals are more ideal candidates for flexible electronics, which allow organic materials to approach their ultimate intrinsic properties. [14,15] Moreover, it has been shown that introducing strain in organic single crystals can further enhance the device performance by suppressing molecular vibrations or shortening π-π distances. [16,17] However, the fabrication of large-area organic single crystals on polymer substrates generally used in flexible devices is encountering huge challenges. On the one hand, commonly hydrophobic polymer substrates result in a limited spreading area of the molecular solution, which hinders the large-area assembly of organic crystals. [18,19] Also, due to the generally good solubility of polymers, the prolonged assembly time may cause damage to the underlying polymer substrate. On the other hand, the growth of large-area organic single crystals requires sophisticated assembly strategies. [20][21][22][23] The currently well-developed technologies include solution Bendable organic single crystals are promising candidates for flexible electronics owing to their superior charge-transport properties. However, large-area high-quality organic single crystals are rarely available on the polymer substrates generally used in flexible electronics. Here, a surfaceassisted assembly strategy based on a polymer modification, poly(amic acid) (PAA), is developed to grow large-area organic singe crystals on polymer substrates using a simple drop-casting method. The unique surface properties of PAA that enable molecular solution superwetting and promote molecular ordered assembly produce an extraordinary self-driven "meniscusguided coating" behavior, enabling the fabrication of millimeter-sized, highly aligned organic single crystals for a variety of organic semiconductors. Organic field-effect transistors based on a mode molecule of 2,7-dioctyl[1] benzothieno[3,2-b][1]benzothiophene demonstrate the highest (average) mobility of 18.6 cm 2 V −1 s −1 (15.9 cm 2 V −1 s −1 ), attractively low operating voltage of −3 V, and high flexible durability. The results shed light on the large-area fabrication of organic single crystals on polymer dielectrics toward high-performance and integrated plastic electronics.

Three-Dimensional Anisotropic Carrier Mobility and Structure–Property Relationships for [1]Benzothieno[3,2-b][1]benzothiophene Derivatives: A Theoretical Study

“…In previous studies, 2,7-dioctyl [1]­benzothieno­[3,2- b ]­[1]­benzothiophene (C 8 -BTBT) was found exhibiting a high hole mobility in OFET, − which is increased about 2–3 orders of magnitude compared with that of BTBT (0.032 cm 2 ·V –1 ·s –1 ). To better understand the role of alkyl substitution in the BTBT derivative, we compared the λ h and λ e values of BTBTT6 with the ones of TBTBT .…”

Stimuli-responsive flexible organic crystals

“…However, organic crystals generally have larger band gaps and lower charge carrier populations than inorganic ones. 140 In addition, the rigid structure of organic crystals will lead to certain limitations in the field of flexible electronics. Therefore, it is necessary to develop molecular crystals that possess both high electrical conductivity and high flexibility for practical applications.…”

Mechanistic study on the structure–property relationship of flexible organic crystals

“…Traditional crystalline materials often suffer from their poor ability of resisting external forces without fragmentation, which greatly hinders their application in flexible devices. Recently, the discovery of flexible organic crystals has remedied this deficiency, and they have attracted numerous attention in the fields of flexible field-effect transistors, 1 wearable devices, 2 flexible displayers, 3 etc. Depending on the type of response to external forces, deformation can be classified into elastic reversible deformation and plastic irreversible deformation.…”