Benzyl viologen as an n-type dopant for organic semiconductors

Abstract

This paper reports an n-type dopant, neutral benzyl viologen (BVo), for organic semiconductors and their application as active layers in organic field-effect transistors (OFETs). BVo is blended in four commonly used n-type and ambipolar conjugated polymer solutions as charge transfer dopant. Electron mobility increased markedly to similar to 10(-1) cm(2) V-1 s(-1) from similar to 10(-3) cm(2) V-1 s(-1) for BVo doped (6.7%v/v) ambipolar diketopyrrolopyrrole-thieno [3,2-b]thiophene (DPVF-TT) OFETs; whereas, only decreased off current was observed in BVo doped (6.7%v/v) n-type OFETs based on strong electron transport polymers, including poly [[ N, N 9-bis(2-octyldodecy1)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-cdt-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 BVo doping efficiency is strongly dependent on conjugated polymer structural differences and transport profiles as well as the interaction between their molecules and BVo during the doping process.