Luminescent High‐Mobility 2D Organic Semiconductor Single Crystals

Abstract

Abstract2D organic semiconductor single crystals comprising one or a few molecular layers of macroscopic lateral sizes are ideal materials for ultrathin, flexible, and transparent field‐effect devices—a platform for transistors and sensors. In recent years, these 2D materials have demonstrated high performance not inferior to their 3D counterparts. However, light emissive properties of 2D organic semiconductor single crystals have not yet been reported, and a combination of high charge‐carrier mobility and bright luminescence in one material is still a challenge for 2D organic optoelectronics. Emissive high‐mobility 2D organic semiconductor based on a [1]benzothieno[3,2‐b]benzothiophene (BTBT)‐derivative, 2,7‐bis(4‐decylphenyl)[1]benzothieno[3,2‐b][1]benzothiophene (DPBTBT), is presented here. DPBTBT molecules self‐organize in large‐area ultrathin single‐crystalline films consisting of one or a few molecular layers. These 2D single crystals perfectly suit as an active layer of organic field‐effect transistors in full accordance with Shockley's model and uniquely combine the high charge‐carrier mobility reaching 7.5 cm2 V–1 s–1 with prominent light emissive properties, which allow a demonstration of the first 2D organic light‐emitting transistor. The high charge‐carrier mobility and thermal stability of the crystalline phases, pronounced luminescence, and good shelf‐life stability suggest that emissive BTBT‐type molecules are a promising avenue for 2D organic optoelectronics.

Luminescent 2D single crystals of thiophene–phenylene co-oligomers for field-effect devices

“…S22–S25) are 8-shaped and show a relatively low axis ratio (no higher than 3 : 1) indicating that the crystal unit cell includes at least two molecules with different orientations of TDM projections on the crystal plane. 12…”

“…OLETs were characterized as described in ref. 12. Briefly, light emission was captured using a microscope equipped with a CCD-camera (Infinity 3, Luminera) at an exposition time of 60 s during transfer characteristics measurement.…”

“…10 To promote the formation of macroscopic 2D single crystals on a substrate via solution processing, long alkyl substituents usually should be attached to the rod-like conjugated core. 3,4,11,12…”

Synthetic approach for the control of self-doping in luminescent organic semiconductors

“…However, the latter is inapplicable for materials unstable under the sublimation conditions, for instance, linear conjugated molecules with long alkyl-chains. 43 Here we report the approach allowing us to control the luminescent properties by mixing the samples obtained via two synthetic pathways differing in the sequence of stages and self-dopant concentration. We designed a co-oligomer 1,2-bis(5-(4octylphenyl)thiophen-2-yl)ethene (C8-BPTE) which can be synthesized by either a cross-coupling reaction or a McMurrey condensation at the last synthetic stage.…”

“…However, the latter is inapplicable for materials unstable under the sublimation conditions, for instance, linear conjugated molecules with long alkyl-chains. 43…”