TY - JOUR
T1 - Sub-Band Filling and Hole Transport in Polythiophene-Based Electrolyte-Gated Transistors
T2 - Effect of Side-Chain Length and Density
AU - Cho, Kyung Gook
AU - Adrahtas, Demetra Z.
AU - Lee, Keun Hyung
AU - Frisbie, C. Daniel
N1 - Publisher Copyright:
© 2023 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
PY - 2023/9/12
Y1 - 2023/9/12
N2 - The relationship between hole density and conductivity in electrochemically gated polythiophene films is examined. The films are integrated into electrolyte-gated transistors (EGTs), so that hole accumulations can be electrochemically modulated up to ≈0.4 holes per thiophene ring (hpr). Polythiophenes include poly(3-alkylthiophenes) (P3ATs) with four different side chain lengths – butyl (P3BT), hexyl (P3HT), octyl (P3OT), or decyl (P3DT) – and poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) and poly(3,3′′′-didodecyl[2,2′:5′,2′′:5′′,2′′′-quaterthiophene]-5,5′′′-diyl) (PQT). Analysis of the drain current – gate voltage (ID–VG) and gate current – gate voltage (IG–VG) characteristics of the EGTs reveals that all six polythiophene semiconductors exhibited reversible conductivity peaks at 0.12 – 0.15 hpr. Conductivity is suppressed beyond ≈0.4 hpr.The maximum carrier mobilities of the P3AT semiconductors increase, and hysteresis of the conductivity peaks decreases, with increasing alkyl side-chain length. PBTTT and PQT with reduced side chain densities exhibit the largest hysteresis but have higher hole mobilities. The results suggest that at ≈0.4 hpr, a polaronic sub-band is filled in all cases. Filling of the sub-band correlates with a collapse in the hole mobility. The side-chain dependence of the peak conductivity and hysteresis further suggests that Coulombic ion-carrier interactions are important in these systems. Tailoring ion-carrier correlations is likely important for further improvements in transport properties of electrochemically doped polythiophenes.
AB - The relationship between hole density and conductivity in electrochemically gated polythiophene films is examined. The films are integrated into electrolyte-gated transistors (EGTs), so that hole accumulations can be electrochemically modulated up to ≈0.4 holes per thiophene ring (hpr). Polythiophenes include poly(3-alkylthiophenes) (P3ATs) with four different side chain lengths – butyl (P3BT), hexyl (P3HT), octyl (P3OT), or decyl (P3DT) – and poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) and poly(3,3′′′-didodecyl[2,2′:5′,2′′:5′′,2′′′-quaterthiophene]-5,5′′′-diyl) (PQT). Analysis of the drain current – gate voltage (ID–VG) and gate current – gate voltage (IG–VG) characteristics of the EGTs reveals that all six polythiophene semiconductors exhibited reversible conductivity peaks at 0.12 – 0.15 hpr. Conductivity is suppressed beyond ≈0.4 hpr.The maximum carrier mobilities of the P3AT semiconductors increase, and hysteresis of the conductivity peaks decreases, with increasing alkyl side-chain length. PBTTT and PQT with reduced side chain densities exhibit the largest hysteresis but have higher hole mobilities. The results suggest that at ≈0.4 hpr, a polaronic sub-band is filled in all cases. Filling of the sub-band correlates with a collapse in the hole mobility. The side-chain dependence of the peak conductivity and hysteresis further suggests that Coulombic ion-carrier interactions are important in these systems. Tailoring ion-carrier correlations is likely important for further improvements in transport properties of electrochemically doped polythiophenes.
KW - carrier localization
KW - charge transports
KW - electrolyte-gated transistors
KW - polaron
KW - sub-band filling
KW - thiophene polymers
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U2 - 10.1002/adfm.202303700
DO - 10.1002/adfm.202303700
M3 - Article
AN - SCOPUS:85159609193
SN - 1616-301X
VL - 33
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 37
M1 - 2303700
ER -