Solution Processable Pseudo n-Thienoacenes via Intramolecular S···S Lock for High Performance Organic Field Effect Transistors

Abstract

New solution processable 3,5-dithioalkyl dithienothiophene (DSDTT) based small molecular semiconductors end functionalized with various (fused) thiophenes including dithienothiophene (DTT), thienothiophene (TT), and thiophene (T) are synthesized and characterized in organic field effect transistors (OFETs). The new DSDTT core was synthesized via a one-pot [1 + 1 + 1] methodology. For comparison, non-thiolated 3,5-dialkyl dithienothiophene (DRDTT) based molecules are also prepared and characterized. Optical, electrochemical, and computed electronic structures of these molecules are investigated and contrasted. Single crystal data support evidence of S­(alkyl)···S­(thiophene) intramolecular locks, with a very short intramolecular S–S distance of 3.17 Å, planarizing the structure as for the equivalent extended n-thienoacenes. Via a solution-shearing semiconductor film deposition method, these semiconductors exhibit a OFET hole mobility up to 2.6 cm2 V–1 s–1, the greatest reported to date for fused/all-thiophene based small molecular organic semiconductors.

Optimizing the self‐assembly of conjugated polymers and small molecules through structurally programmed non‐covalent control

“…However, systems possessing more than five fused rings are difficult to synthesize and have poor solubility. In response to this challenge, Vegiraju et al recently implemented conformational locks in a series of fused thiophene oligomers (Figure 10) to achieve some of the highest hole mobilities reported for this class of compounds 152 . Alkylthiol substituents rendered dithienothiophene oligomers planar, akin to completely fused undeca‐thienoacenes, through chalcogen bonds between the substituents and main‐chain sulfur atoms.…”

“…Chemical structure and crystal packing of pseudo n ‐thienoacenes developed by Vegiraju et al Reproduced with permission 152 . Copyright 2020, American Chemical Society…”

Thienoisoindigo (TII)‐Based Quinoidal Small Molecules for High‐Performance n‐Type Organic Field Effect Transistors

“…OSC films were fabricated by solution shearing, considering that it is a reliable technique for enhancing thin film crystallinity and promoting alignment, thus enhancing charge mobility versus isotropic/fast spin‐coating process. [ 54,74–75 ] Bottom‐gate top‐contact (BGTC) FET device architecture based on solution‐sheared films were fabricated for evaluating the charge transport characteristics. Remarkably, our results revealed that TIIQ‐b16‐ based OFETs exhibited excellent n‐channel electrical performance, with an electron μ as high as 2.54 cm 2 V −1 s −1 and a current ON/OFF ratio ( I ON /I OFF ) > 10 5 –10 6 .…”

Solution‐Processable Multifused Thiophene Small Molecules and Conjugated Polymer Semiconducting Blend for Organic Field Effect Transistor Application

“…The design of small molecular organic semiconductors should include a highly planar conjugated core for efficient charge transport, favorable intermolecular π–π stacking, and the presence of alkyl chains, which increases solubility and enables solution processability. Among the various conjugated building blocks that have been developed, fused thiophenes, such as thienothiophene (TT), dithienothiophene (DTT), and tetrathienoacene (TTA), have received extensive attention due to their structural planarity and strong intermolecular S···S interactions, which promote intramolecular and intermolecular π–π stacking, [ 21–28 ] and thus superior carrier transfer efficiency. [ 29,30 ] Therefore, utilization of these units in the design of new solution processable organic semiconductors for OFET applications is highly desirable.…”