N-Alkyl substituted 1H-benzimidazoles as improved n-type dopants for a naphthalene-diimide based copolymer

Abstract

Alkyls in 1H-benzimidazoles influence their intercalation within a naphthalene diimide-based copolymer, thus affecting the electrical conductivity.

Electron transport in a sequentially doped naphthalene diimide polymer

“…31 Although it has been widely used as an n-dopant for NDI polymers including P(NDIOD-T2), both its limited reactivity, likely originating from a slow endergonic hydride-transfer step, and poor miscibility with some polymers 25 have proven obstacles, with thermal annealing often being used to address the former issue. 23,24,32 The dimer (RuCp*mes) 2 , on the other hand, is strongly reducing and reacts cleanly with the loss of two electrons to form RuCp*mes + ; 33 it has been previously co-deposited with P(NDIOD-T2) to afford conductivity values up to 10 À3 S cm À1 . 34 We have previously reported that a DMBI dimer is a more effective dopant for P(NDIOD-T2) than its DMBI-H analogue.…”

“…Poor electrical conductivity of PNBS after attempted doping with N-DMBI-H is consistent with the optical data and with some previous reports on concomitant doping that indicate thermal treatments are needed to initiate doping reactions. 25,32 In previous reports, (RuCp*mes) 2 was found to be suitable for concomitant doping of P(NDIOD-T2), 34 but unsuitable for sequentially doping the same polymer, this unsuitability being attributed to the inability of the dopant to enter the ordered (face-on) film. 11 In the present case, the reaction clearly occurs, as shown by optical and GIXRD data; presumably the low conductivity results from the disruption of the film packing.…”

Principles of Structural Design of Conjugated Polymers Showing Excellent Charge Transport toward Thermoelectrics and Bioelectronics Applications

“…They suggest that increasing the length and branching in the alkyl substituent can improve the miscibility between the dopant and the polymer. 4‐(1,3‐Dimethyl‐2,3‐dihydro‐1H‐benzo[d]imidazol‐2‐yl)‐ N , N ‐diisopropylaniline (DiPrBI) doped samples were reported to achieve an electrical conductivity of 7.2∙10 −3 , a Seebeck coefficient of −32 ± 15 µV K −1 and PF of 1.1∙10 −3 μW m −1 K −2 at 363 K …”

Impact of Singly Occupied Molecular Orbital Energy on the n-Doping Efficiency of Benzimidazole Derivatives

“…29 The low conductivity was attributed to the strong charge carrier localization on the polymer backbone 35 and to the limited solubility of benzimidazole-based dopants in the host polymer, which restricts the doping efficiency to only ∼1%. 36 Following that study, many reports have focused on improving the miscibility of the dopant, by tailoring either the host polymer backbone [37][38][39][40][41][42] or the dopant molecular structure. 36 Despite the progress in this field, the role of the benzimidazole-based dopant energetics on the doping efficiency remains poorly understood.…”