Studies Of Electrical Charge Transport In A High-mobility Semiconducting Polymer

Semiconducting polymers are promising semiconductor materials for flexible electronics with the advantages of solution processability,low cost and flexibility.The organic electronics include organic field-effect transistors,organic solar cells,and organic light-emitting devices.Their properties mainly depend on the charge transport properties of organic semiconductors.Despite the mobilities of semiconducting polymers have increased dramatically in recent years,the relationship between their microstructure and charge transport properties is not fully under-stood yet.Semicrystalline polymers such as P3HT and PBTTT have high crystalline microstructure and adopt edge-on molecular packing,therefore they show high mobilities above 1 cm²V^-1s^-1at ultrahigh carrier density(¹0²11 cm^-3).Indacenodithiophene-co-benzothiadiazole（IDTBT）exhibits surprisingly high mobilities due to its low energetic disorder,despite that it shows less crystalline order.In Cytop-gated IDTBT devices,high mobilities above 1.2 cm²V^-1s^-1were achieved at low carrier density(¹0¹11 cm^-2).At such low carrier density,it is difficult to achieve such high mobilities in P3HT and PBTTT devices.To better understand charge trans-port properties of high mobility semiconducting polymers,a detailed investigation on IDTBT is necessary.In this thesis,vacuum（ε=1）was applied as the gate insulator of IDTBT FETs for the first time.Vacuum-gap IDTBT FETs show high mobilities approaching 0.9 cm²V^-1s^-1.To the best of our knowledge,it is the highest reported mobility of vacuum-gap polymer transistors.We also studied the influence of gate insulators on the mobilities of IDTBT using Cytop and P（VDF-TrFE-CFE）as top gate.Our result suggests that charge carrier concentration and dipolar disorder induced by polar insulator layer both play an important role in determining the mobility of the IDTBT transistors.