Benzyl viologen as an n-type dopant for organic semiconductors

Abstract

Abstract This paper reports an n-type dopant, neutral benzyl viologen (BV0), for organic semiconductors and their application as active layers in organic field-effect transistors (OFETs). BV0 is blended in four commonly used n-type and ambipolar conjugated polymer solutions as charge transfer dopant. Electron mobility increased markedly to ∼10−1 cm2 V-1 s-1 from ∼10−3 cm2V−1s−1 for BV0 doped (6.7%v/v) ambipolar diketopyrrolopyrrole-thieno [3,2-b]thiophene (DPPT-TT) OFETs; whereas, only decreased off current was observed in BV0 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 BV0 doping efficiency is strongly dependent on conjugated polymer structural differences and transport profiles as well as the interaction between their molecules and BV0 during the doping process.