Naphthodithiophenediimide–Benzobisthiadiazole-Based Polymers: Versatile n-Type Materials for Field-Effect Transistors and Thermoelectric Devices

Abstract

New π-conjugated polymers with strong electron affinity, PNDTI-BBTs, consisting of naphtho[2,3-b:6,7-b′]dithiophenediimide (NDTI) and benzo[1,2-c:4,5-c′]bis[1,2,5]thiadiazole (BBT) units, were synthesized. PNDTI-BBTs have low-lying LUMO energy levels (∼−4.4 eV), which is sufficiently low for air-stable electron transport in organic field-effect transistors and for being readily doped by a well-known n-dopant, N,N-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole (N-DMBI), affording doped polymer films with relatively high conductivities and Seebeck coefficients. Depending on the solubilizing alkyl groups (2-decyltetradecyl, PNDTI-BBT-DT, or 3-decylpentadecyl groups, PNDTI-BBT-DP), not only the electron mobility in the transistor devices with the pristine polymer thin films (PNDTI-BBT-DT: ∼0.096 cm2 V–1 s–1; PNDTI-BBT-DP: ∼0.31 cm2 V–1 s–1) but also the conductivity and power factor of the doped thins films (PNDTI-BBT-DT: ∼0.18 S cm–1 and ∼0.6 μW m–1 K–2; PNDTI-BBT-DP: ∼5.0 S cm–1 and ∼14 μW m–1 K–2) were dr...