Nitrogenous Interlayers for ITO S/D Electrodes in N‐Type Organic Thin Film Transistors

Abstract

The commercialization of organic thin film transistors (OTFTs) is partly hindered by the high cost and stubborn work function (WF) of common Au source/drain (S/D) electrodes. In this work, indium tin oxide (ITO) S/D electrodes modified with three different nitrogenous interlayers including 1,4‐bis(2‐hydroxyethyl) piperazine (HEP), polyethylenimine ethoxylated (PEIE), and branched polyethylenimine (PEI) are adopted to fabricate n‐type OTFTs. The WF of bare ITO is 4.7 eV, whereas ITO modified with nitrogenous interlayers exhibits WFs ranging from 4.1 to 3.6 eV. By the first‐principle calculation and element analysis, the protonated amines are critical for the reduction of ITO surface WF. Besides, the interlayers with higher nitrogen contents are more likely to improve the wettability of octadecyltrichlorosilane (OTS) modified ITO substrates, and help to gain the continuous and oriented poly[2,5‐bis(4‐tetradecyloctadecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione‐alt‐5,5′‐di(thiophen‐2‐yl)‐2,2′‐(E)‐1,2‐bis(3,4‐difluorothien‐2‐yl)‐ethene] (P4FTVT‐C32) semiconductor thin films. Therefore, P4FTVT‐C32 based OTFTs with maximum electron field‐effect mobility of 1.95 cm2 V−1 s−1 are achieved by PEI treatments. These results indicate that the ITO S/D electrodes modified by nitrogenous interlayers can greatly slash costs and promote commercialization of OTFTs.

High-performance organic thin-film transistors: principles and strategies

“…3b), and modified indium tin oxide (ITO) S/D electrodes in 2022. 52 The chemical structure of P4FTVT-C32, with À5.4 eV for the HOMO and À3.5 eV for the LUMO, characterizes it as an ambipolar semiconductor polymer, as depicted in Fig. 3b.…”

Complementary Inverter Based on n‐Type and p‐Type OFETs with the Same Ambipolar Organic Semiconductor and ITO S/D Electrodes

“…Polymers containing simple aliphatic amine groups with large band‐gap physisorbed onto the surface is a simpler modification method for reducing the WF of metal and metal oxide conductors. [ 31–34 ] After the WF is adjusted to the range of 3.50–5.60 eV, ITO can well match most organic semiconductors (OSCs). [ 17–34 ]…”

“…[ 31–34 ] After the WF is adjusted to the range of 3.50–5.60 eV, ITO can well match most organic semiconductors (OSCs). [ 17–34 ]…”

“…Polymers containing simple aliphatic amine groups with large band-gap physisorbed onto the surface is a simpler modification method for reducing the WF of metal and metal oxide conductors. [31][32][33][34] After the WF is adjusted to the range of 3.50-5.60 eV, ITO can well match most organic semiconductors (OSCs). [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Second, we hope to find one kind of organic semiconductor, instead of necessary two kinds, to construct n-type and p-type OFETs simultaneously.…”

“…[31][32][33][34] After the WF is adjusted to the range of 3.50-5.60 eV, ITO can well match most organic semiconductors (OSCs). [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Second, we hope to find one kind of organic semiconductor, instead of necessary two kinds, to construct n-type and p-type OFETs simultaneously. Organic ambipolar materials are the preferred for their characteristics of exhibiting n-type performance in OFETs constructed with low WF S/D electrodes, [34] while exhibiting p-type performance in OFETs constructed with high WF S/D electrodes.…”