High performance and stable naphthalene diimide based n-channel organic field-effect transistors by polyethylenimine doping

•High performance and air stable n-channel OFETs is achieved by PEI doping.•The doped OFETs exhibit significantly improved performance.•The low molecular weight PEI shows better doping efficiency than high molecular weight PEI.

In this paper, we study the effect of the structure and molecular weight of polyethylenimine (PEI) on doping efficiency of n-type organic semiconductors based on 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)). Linear and branched PEI with low (Mw = 2 and 3 kDa) and high molecular weights (Mw = 25 kDa) are used. It is found that the low molecular weight PEI shows higher doping efficiency than high molecular weight PEI due to better mix-ability between the dopant and the host. Doped P(NDI2OD-T2) OFETs show highly improved mobility up to 0.85 cm2/V·s (linear) at 0.1 wt% doping concentration from 0.21 cm2/V·s for pristine devices with enhanced air and operational stability.

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