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Study On Long-term Air Stable N-type Polymer Field-effect Transistors

Posted on:2020-01-20Degree:MasterType:Thesis
Country:ChinaCandidate:F F WangFull Text:PDF
GTID:2428330578962366Subject:Materials engineering
Abstract/Summary:PDF Full Text Request
D-A conjugated polymers represent a class of promising semiconducting materials for organic field effect transistors.They have also attracted considerable attention due to their attractive advantages such as variety molecular designs,easy tuned energy levels,solution-processability,etc.Isoindigo and its derivatives have good planarity and excellent solubility and great OFETs performances.The LUMO/HOMO energy level of the molecule can be regulated by introducing N atoms on the donor,and polymers were synthesized with different donors.The OFETs behavior long-term stable electron transport in air.In this paper,three polymers were designed and synthesized,and a series of studies on their thermal stability,optical properties,electrochemical properties,electrical properties of OFETs and air stability were investigated.The main work of this paper is as follows:?1?We use fluorinated bithiophene as a donor,and BIBDF?P1?and BABDF?P2?as acceptor units to develop air-stable and unipolar electron transport polymer semiconductors.Unencapsulated OFETs based on P1 and P2 were fabricated and directly evaluated under air conditions.The highest effective mobility of 0.23 cm2V–1s–1 was obtained for P2-based devices with high Ion/Ioff ratio>106 and low threshold voltage of1.1 V.Moreover,P2 had high air stability and maintained unipolar electron transport with the highest effective mobility of up 0.1 cm2V–1s-1 and Ion/Ioff ratio>106 during the 60 days of air storage.?2?Aza-heterocycle?BABDF?-based polymer was designed and synthesized using weak acceptor dithiazole?TZ?as co-units.PBABDF-TZ obtained the deep unoccupied molecular orbital?LUMO?/highest occupied molecular orbital?HOMO?energy levels of-4.28/–6.06 eV by introducing TZ.These levels are low enough for air-stable electron transport and large enough for the hole injection barriers in OFETs.Consequently,the unencapsulated bottom-gate/top-contact?BG/TC?devices exhibited unipolar electron transport under air conditions.Furthermore,these devices had high air stability and maintained unipolar electron transport with a mobility of up to 0.01cm2V–1s–1 during the one-year characterization period.
Keywords/Search Tags:organic field-effect transistors, D-A conjugated polymers, LUMO/HOMO energy levels, electron mobility, air stability
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