Fet transistor vs vacuum12/18/2023 ![]() ![]() The advantage of 12 is that long alkyl groups can be attached at the N-position to increase the solubility in solvents. Instead of the thiophene rings, pyrrole rings were introduced to synthesize 12. The high air stability is ascribed to the lower HOMO level. The mobility is comparable to that of pentacene. The device was fabricated by vacuum deposition and it was stable in air. Higher mobility of 2.9 cm 2 Vs −1 was reported using 11. The mobility was dependent on the alkyl chain length and the highest mobility of 2.75 cm 2 Vs −1 was achieved in the compound with C 13H 27 groups. Interestingly, alkyl-substituted derivatives 10 resulted in high-performance FETs fabricated by the solution method. The stability was discussed based on the molecular orbital calculations. The device was stable for several months in air. In 8, the selenium-containing form showed enhanced mobility of 0.2 cm 2 Vs −1, whereas even higher mobility of 2.0 cm 2 Vs −1 was measured in sulfur-containing 9. These facts suggest that skeletal modification strongly affects electronic properties.Īs new semiconductors, Takimiya et al developed diphenyl-substituted tri- or tetra-cyclic systems 8 and 9. The mobility of 6 (0.011 cm 2 Vs −1) is lower than that of its isomer 7 (0.12 cm 2 Vs −1). Compound 5, composed of only thiophene rings, shows lower mobility (0.045 cm 2 Vs −1). Compounds 5– 7 containing more thiophene rings were developed. The mobility of tetracene analogue 4 is 0.1 cm 2 Vs −1, indicating that systems with more conjugation show higher mobilities. The air stability is improved compared to pentacene. Thiophene-containing compound 3 exhibits high mobility of 0.31 cm 2 Vs −1 and low threshold voltage (7 V). Replacement of the benzene rings of pentacene by thiophene rings also enhances the air stability. The mobility in air (1.1 cm 2 Vs −1) is higher than in vacuum. Picene 2, an isomer of pentacene, is stable in air because of the phenanthrene-type structure leading to the lower HOMO level. To overcome those disadvantages, various pentacene derivatives and analogues have been developed and the FETs based on them have been fabricated. Good solubility is crucial for device fabrication using solution methods such as inkjet printing. ![]() However, pentacene has disadvantages such as instability in air and low solubility in solvents. Pentacene 1 shows the highest hole mobility of 3.0 cm 2 Vs −1 in thin-film OFETs. In this review, new organic semiconductors suitable for high-performance FETs are described, and the relationship between the transistor characteristics and chemical structure is discussed. These materials make OFETs more attractive, and applications using them have been attempted. Recently, organic semiconductors have been developed exhibiting mobilities comparable to those of amorphous silicon. To achieve such performance, development of new organic semiconductors as well as the improvement of device structure is important. In addition, high stability in air is essential for applications. Good transistor performance means high mobility, large on/off ratio and low threshold voltage. Device characteristics are evaluated mainly by the carrier mobility, on/off current ratio and threshold voltage. An insulator layer, such as SiO 2, exists between the gate electrode and organic semiconductor. It includes source, drain and gate electrodes, and an active layer of organic semiconductor. The OFETs have a simple structure shown in figure figure1. ![]() Organic FETs have great perspectives in electronics. ![]() Modification of organic semiconductors can easily tune the transistor characteristics. Using solution techniques such as spin coating, inkjet printing and screen printing, large-area fabrication is possible at low costs. Organic semiconductors can be processed at low temperatures compatible with plastic substrates, whereas higher temperatures are required for alternative Si-based FETs. Organic field-effect transistors (OFETs) have been of great interest for applications, such as display drivers, identification tags and smart cards, because they have advantages of low cost, flexibility and light weight. ![]()
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |