Benzyl viologen as an n-type dopant for organic semiconductors

Abstract This paper reports an n-type dopant, neutral benzyl viologen (BV 0 ), for organic semiconductors and their application as active layers in organic field-effect transistors (OFETs). BV 0 is blended in four commonly used n-type and ambipolar conjugated polymer solutions as charge transfer dopant. Electron mobility increased markedly to ∼10 −1  cm 2  V -1  s -1 from ∼10 −3 cm 2 V −1 s −1 for BV 0 doped (6.7%v/v) ambipolar diketopyrrolopyrrole-thieno [3,2-b]thiophene (DPPT-TT) OFETs; whereas, only decreased off current was observed in BV 0 doped (6.7%v/v) n-type OFETs based on strong electron transport polymers, including poly [[ N , N 9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]- alt -5,59-(2,29-bithiophene)] (P(NDI2OD-T2)), poly{2,5-bis(2-dodecylhexadecyl)-3,6-di(thiophen-2-yl)pyrrolo-[3,4- c ]pyrrole-1,4(2H, 5H)-dione-alt-(E)-1,2-bis(3-cyanothiophen-2-yl)ethene} (2DPP-2CNTVT) and poly{2,5-bis(7-dodecylhenicosyl)-3,6-di(thiophen-2-yl)pyrrolo-[3,4- c ]pyrrole-1,4(2H, 5H)-dione-alt-(E)-1,2-bis(3-cyanothiophen-2-yl)ethene (7DPP-2CNTVT). This indicates that BV 0 doping efficiency is strongly dependent on conjugated polymer structural differences and transport profiles as well as the interaction between their molecules and BV 0 during the doping process.