Phosphonic Acid Self-assembeld Monolayers (SAMs) Applied In N-type Organic Field-effect Transistors (OFETs)

Organic field-effect transistors(OFETs) have many advantages over inorganic field-effect transistors because they were manufactured with organic materials, those advantages including easier to process and manufacture, can be prepared on flexible substrate and so forth, which endow OFETs a bright application prospect in organic electronics. Nevertheless, there are many problems to be solved before OFETs are produced and applied in a large-scale, for instance, interface engineering problems and n-type organic semiconductor(OSC) materials of high performance and air stability are still very scarce. The work elaborated in this dissertation was a try to address these challenges, and in general this dissertation covers the following aspects:Firstly, the invention background, research history, application prospect and difficulties in research of OFETs were introduced; the basic configurations of OFETs were depicted and merits and demerits of each configuration was compared; the working modes of OFETs, the transporting mechanism of carrier in OSC and the characteristic curve and some key performance parameters of OFETs were elucidated; and then some typical materials of three types of OSC, self-assembeld molecules and its application in OFETs were explicated.Secondly, after a deep understanding of the self-assembeld molecular structures, two kinds of phosphonic acid were designed and synthesised(NaPA and AnPA), and then 4 kinds of phosphonic acid self-assembeld monolayers(SAMs) were prepared on the SiO2 surface respectively with T-BAG(tethering by aggregation and growth) method. Then the mechanism of phosphonic acid self-assembeling on the SiO2 surface was interpreted. The contact angle observation and AFM characterization were carried out to verify the exsistence of SAMs and the changes it brought to the SiO2 surface.Finally, on the basis of literature investigation and understanding of perylene diimide(PDI) molecular structure, 5 perylene diimide derivatives were designed and synthesized(PDI-8C, PDI-i8 C, PDI-14 C, PDI-CY5 and PDI-PhCN); Then OFETs based on those perylene diimide derivatives were fabricated with thermal evaporation method; after a semiconductor property characterization, the the characteristic curve and some key performance parameters(like carrier mobility) were obtained, and the effects of SAMs and substrate temperature(annealing temperature) on the performance of OFETs were analysised and discussed, the conclusion was backed with AFM characterization; at last, the relation between perylene diimide molecular structure and its semiconductor properities were discussed.