Incorporation of Selenopheno[3,2-b]pyrrole into Benzothiadiazole-Based Small Molecules for Organic Field-Effect Transistors

Abstract

Incorporating selenophene into organic semiconductors has recently shown promising results in both organic solar cells (OSCs) and organic field-effect transistors (OFETs). In most studies, replacing thiophene with selenophene has improved the performance in OSCs and OFETs. However, some other reports do not show the same trend. Therefore, the structure−property relationship of selenophene-containing semiconducting materials is still to be investigated and understood. On the other hand, reports have shown that thiophene flanked benzothiadiazole-and thieno-[3,2-b]pyrrole-based donor−acceptor−donor molecular architecture gave a banana-shaped small organic conjugated molecule with moderate OFETs performance. To understand the structure− property relationship and influence on OFETs performance, by replacing thiophene with selenophene in chalcogenopheno[3,2-b]pyrrole, we report a nonconventional fused ring system, estermonocapped selenopheno[3,2-b]pyrrole, which was coupled with chalcogenophene spacer flanked benzothiadiazole to yield two curved small organic conjugated molecules, diethyl 2,2′-(5,5′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis(thiophene-5,2-diyl))bis(4dodecyl-4H-selenopheno[3,2-b]pyrrole-5-carboxylate (BT-2T-2SeP) and diethyl 2,2′-(benzo[c][1,2,5]thiadiazole-4,7-diylbis-(selenophene-5,2-diyl))bis(4-dodecyl-4H-selenopheno[3,2-b]pyrrole-5-carboxylate (BT-2Se- 2SeP). This is the first report of selenopheno [3,2-b]pyrrole incorporated in donor−acceptor small conjugated organic molecules for OFETs applications. BT-2T-2SeP and BT-2Se-2SeP exhibited comparable maximum hole mobilities of 8.82 × 10 −3 cm 2 V −1 s −1 and 1.44 × 10 −2 cm 2 V −1 s −1 , respectively. Furthermore, these molecules exhibited lower threshold voltages between 0-(−5) V and high on−off current ratios of 10 4 and ∼10 5 , respectively, for BT-2T-2SeP and BT-2Se-2SeP.

Linear-Shaped Low-Bandgap Asymmetric Conjugated Donor Molecule for Fabrication of Bulk Heterojunction Small-Molecule Organic Solar Cells

“…Alternatively, two rigid nitrogen atoms in the BTD ring form hydrogen bonds with the adjacent atoms to improve the molecular backbone’s planarity [ 25 ]. Many BTD-containing polymers and small molecules have been widely used in several organic electronic applications, such as solar cells, organic light-emitting diodes (OLEDs), and organic field-effect transistors (OFETs) [ 26 , 27 , 28 ]. However, thiophene and oligothiophene derivates have been extensively studied as donor units for developing small organic molecules owing to their ease of synthesis, superb stability, and excellent hole/electron transport characteristics [ 29 , 30 , 31 ].…”

Siloxane Side-Chain-Modified Diketopyrrolopyrrole and Thienopyrrole Containing Small Molecules for Organic Field-Effect Transistors

“…Organic semiconducting materials (OSMs) gained attention within the last few decades due to their relatively low cost, light weight, flexibility, and tunable optoelectronic properties. − OSMs are used in organic field-effect transistors (OFETs), light-emitting diodes, solar cells, photodetectors, memory devices, chemical sensors, logic circuits, etc . Among organic electronic devices, OFETs are essential components in analog and digital integrated circuits. − OSMs are categorized into two types depending on their molecular backbone structure and molecular weight: small organic semiconducting molecules and semiconducting polymers.…”

“…33 Our group reported TP-based semiconducting materials with reasonable hole mobilities for small molecules 22 [1,2,5]thiadiazole (BT)-and TP-based small molecules with different spacer units were reported with hole mobilities in the range of 10 −1 −10 −3 cm 2 V −1 s −1 . 5,21,22,34 Moreover, a diketopyrrolo [3,4-c]pyrrole (DPP)−TP-based copolymer was also reported with a hole mobility of over 10 −1 cm 2 V −1 s −1 . 23,35 In the process of understanding the behavior of TP in semiconductors, especially in small molecules, there is an opportunity to expand our studies incorporating other acceptors, such as DPP.…”

“…25,28 Siloxane side chains also provide additional ambient stability to thin films, which offer an opportunity for processing in ambient conditions. 33 Our group reported TP-based semiconducting materials with reasonable hole mobilities for small molecules 22 [1,2,5]thiadiazole (BT)-and TP-based small molecules with different spacer units were reported with hole mobilities in the range of 10 −1 −10 −3 cm 2 V −1 s −1 . 5,21,22,34 Moreover, a diketopyrrolo [3,4-c]pyrrole (DPP)−TP-based copolymer was also reported with a hole mobility of over 10 −1 cm 2 V −1 s −1 .…”

“…Our group reported TP-based semiconducting materials with reasonable hole mobilities for small molecules (∼0.1 cm 2 V –1 s –1 ). Benzo­[ c ]­[1,2,5]­thiadiazole (BT)- and TP-based small molecules with different spacer units were reported with hole mobilities in the range of 10 –1 –10 –3 cm 2 V –1 s –1 . ,,, Moreover, a diketopyrrolo­[3,4- c ]­pyrrole (DPP)–TP-based copolymer was also reported with a hole mobility of over 10 –1 cm 2 V –1 s –1 . , In the process of understanding the behavior of TP in semiconductors, especially in small molecules, there is an opportunity to expand our studies incorporating other acceptors, such as DPP. Many high-performing donor–acceptor polymers are reported with DPP acceptors, which show excellent hole mobilities. ,, Some DPP-based small molecules are also reported in the literature; however, most of the described DPP-based small molecules are primarily used in organic photovoltaics (OPVs). , DPP-based small molecules with siloxane-terminated side chains were reported with high hole mobility (3.04 cm 2 V –1 s –1 ) by Noh et al, but fabrication and testing were performed under an inert atmosphere.…”