Benzothiadiazole‐Based Small‐Molecule Semiconductors for Organic Thin‐Film Transistors and Complementary‐like Inverters

Abstract

New benzothiadiazole derivatives, 4,7‐bis(5‐phenylthiophen‐2‐yl)benzo[c][1,2,5]thiadiazole (PT‐BTD) and 4,7‐bis[4‐(thiophen‐2‐yl)phenyl]benzo[c][1,2,5]thiadiazole (TP‐BTD), were synthesized and characterized as small‐molecule organic semiconductors for organic thin‐film transistors (OTFTs) and complementary inverters. The thermal, optical, and electrochemical properties of the new compounds were fully characterized. Vacuum‐deposition and solution‐shearing methods were used to fabricate thin films based on these compounds. Thin films based on PT‐BTD exhibited p‐channel characteristics with hole mobilities as high as 0.10 cm2 V−1 s−1 and current on/off ratios >107 for top‐contact/bottom‐gate OTFT devices. With an optimized blending ratio of PT‐BTD and the representative n‐channel semiconductor N,N′‐1H,1H‐perfluorobutyl dicyanoperylenediimide, bulk heterojunction ambipolar transistors were fabricated with balanced hole and electron mobilities of 0.10 and 0.07 cm2 V−1 s−1, respectively. Furthermore, a complementary‐like inverter was fabricated using ambipolar thin‐film transistors, which showed a high voltage gain of 84.

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

“…The π–conjugated system of small molecules efficiently tunes the photophysical properties while lowering the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) [ 16 , 17 , 18 ]. The selection of an appropriate donor–acceptor unit for developing small molecules is very important in the design of semiconducting materials for achieving high electrical properties [ 19 ]. From the molecular design perspective, the optical and energy levels of conjugate molecules can be realistically tuned by substituting different electron donating/accepting groups, such as alkylated bithiophene, alkyl phenyl, and heterocyclic units, in the donor/acceptor backbone [ 20 , 21 , 22 , 23 , 24 ].…”

“…From the molecular design perspective, the optical and energy levels of conjugate molecules can be realistically tuned by substituting different electron donating/accepting groups, such as alkylated bithiophene, alkyl phenyl, and heterocyclic units, in the donor/acceptor backbone [ 20 , 21 , 22 , 23 , 24 ]. The heterocyclic benzothiadiazole (BTD) is believed to be a useful building block in the design of organic electronic materials owing to its higher electron-withdrawing capability, electron affinity (EA), and high stability [ 16 , 17 , 18 , 19 ]. Alternatively, two rigid nitrogen atoms in the BTD ring form hydrogen bonds with the adjacent atoms to improve the molecular backbone’s planarity [ 25 ].…”

A Ladder-Type Organosilicate Copolymer Gate Dielectric Materials for Organic Thin-Film Transistors

“…Among the fundamental components of OTFTs, namely the semiconductor, dielectric, and conductor, studies on the development and application of organic semiconducting materials have intensively been performed for the last few decades [9][10][11][12][13][14][15][16][17][18]. Development of new dielectric materials for OTFTs, which perform as capacitors, insulators, and substrates, is also important to realize various electronic applications based on OTFTs.…”