Electrochemical Investigations of the N-Type Semiconducting Polymer P(NDI2OD-T2) and Its Monomer: New Insights in the Reduction Behavior

Abstract

This manuscript provides the first systematic characterization of the electrochemical properties of the high mobility n-type polymer poly{[N,N′-bis(2octyldodecyl)-naphthalene-1,4,5,8-bis (dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)) and its corresponding monomer 2,6-bis(2-bromothien-5-yl)naphthalene-1,4,5,8-tetracarboxylic-N,N′-bis(2-octyldodecyl) diimide (Br-NDI2OD-T2-Br) by cyclic voltammetry and in situ spectroelectrochemistry. Both monomer and polymer reveal a 2-fold reduction to the dianion via a radical anion species. The comparison between monomeric and polymeric species allows the explanation of the electrochemical behavior of P(NDI2OD-T2) according to redox polymers with localization of charges on the naphthalene bisimide unit. Measurements with electrolyte gated transistors suggest electron hopping transport according to mixed valence conductivity. In the last section of this paper we discuss a significant first cycle effect upon electrochemical reduction which had not been reported for ntype polymers before. The effect is even more pronounced for samples with controlled morphology, that is, high amounts of aggregation in the films. In agreement with solution experiments we attribute the appearance of the signal at −1.04 V (E 1/2 = −1.00 V) to the radical anion form of the solvated species.

Analysis of Conjugated Polymers Conductivity by in situ Electrochemical‐Conductance Method

“…[101,142] Ludwigs et al performed the in-situ conductance characterization of the high mobility n-type polymer poly{[N,N'-bis(2octyldodecyl)-naphthalene-1,4,5,8-bis (dicarboximide)-2,6-diyl]alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)). [143] These results showed that the n-doping follows the electron hopping transport according to mixed valence conductivity theory, since a maxima value of conductance is obtained after the negative charging processes, while in the neutral and the fully charged states the material is (almost) nonconductive. Swager et al synthesized soluble di-cationic poly-(pyridinium-phenylenes)s, these polymers, doped with chloride counterions, present ntype conductivity, (a maximal conductivity around 30 Ω À 1 cm À 1 ).…”

“…Ludwigs et al . performed the in‐situ conductance characterization of the high mobility n ‐type polymer poly{[N,N’‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis (dicarboximide)‐2,6‐diyl]‐alt‐5,5’‐(2,2’‐bithiophene)} (P(NDI2OD‐T2)) . These results showed that the n ‐doping follows the electron hopping transport according to mixed valence conductivity theory, since a maxima value of conductance is obtained after the negative charging processes, while in the neutral and the fully charged states the material is (almost) nonconductive.…”

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

“…The changes are similar to those observed upon electrochemical reduction of P(NDI2OD-T2). 47 OTFT characterisation To examine the doping effect of TBAF on the electrical properties of P(NDI2OD-T2), un-doped and doped polymer layers were investigated in OTFT devices with a top-gate, bottom-contact (TG/ BC) configuration fabricated via solution processing. The transfer characteristics of a set of transistors based on un-doped and doped polymer with representative equivalents of dopant are shown in Fig.…”

Electron Transport and Nanomorphology in Solution‐Processed Polymeric Semiconductor n‐Doped with an Air‐Stable Organometallic Dimer

“…To help clarify these questions, we investigate the electron transport, and nanoscale morphology of organic diodes based on solution‐processed P(NDI2OD‐T2) n‐doped with a moderately air‐stable ruthenium organometallic dimer, (RuCp*Mes) 2 (see Figure a, left) . As noted above, P(NDI2OD‐T2) exhibits trap‐free SCLC electron transport, which can be attributed to it high EA of around 4.0 eV .…”