Solubility‐Limited Extrinsic n‐Type Doping of a High Electron Mobility Polymer for Thermoelectric Applications

Abstract

The thermoelectric properties of a highperformance electron-conducting polymer, (P(NDIOD-T2), extrinsically doped with dihydro-1H-benzoimidazol-2-yl (NDBI) derivatives, are reported. The highest thermoelectric power factor that has been reported for a solution-processed n-type polymer is achieved; and it is concluded that engineering polymerdopant miscibility is essential for the development of organic thermoelectrics.

Efficient and Air‐Stable Mixed‐Cation Lead Mixed‐Halide Perovskite Solar Cells with n‐Doped Organic Electron Extraction Layers

“…Compared with its parent N-DMBI, 4-(1,3-dimethyl-2,3-dihydro-1H-benzimidazol-2-yl)-N,N-diphenylaniline (N-DPBI) has a decreased electron-donating strength of the amine functionality by a substitution of methyl groups with phenyl rings. [31] The aromatic phenyl rings stabilize the radical species through resonance, ensuring a stable doped formulation over time. We dissolved N-DPBI and C 60 in dichlorobenzene and spin-coated the solution in a nitrogen-filled glove box directly on glass or fluorine doped tin oxide (FTO) coated glass to form a thin film.…”

High Seebeck Coefficient and Power Factor in n‐Type Organic Thermoelectrics

“…For example, Schlitz et al have shown that solution mixtures of P(NDIOD-T2) with 9 mol% N-DBI derivatives can achieve σ ≈ 1 S m −1 and a PF over 0.6 µW m −1 K −2 . [11] Yuan et al reported a small-molecule 2DQTT-o-OD that, with 10 wt% of a novel N-DBI derivative incorporated in solution, acquires a PF of 17.2 µW m −1 K −2 at room temperature. [12] Shi et al achieved a high electron mobility in FBDPPV with σ ≈ 1400 S m −1 and PF ≈ 28 µW m −1 K −2 , when adding around 5 wt% N-DMBI in solution.…”

Photoinduced p‐ to n‐type Switching in Thermoelectric Polymer‐Carbon Nanotube Composites

“…[3][4][5][6] One key advantage of this class of materials is their amenability to solution processing, and thus potential for roll-to-roll upscaling. [ 7,8 ] The fully lowcost potential relies, however, on achieving realistic performance while keeping the processing schemes simple, including patterning of different materials.…”

“…For example, extrinsic doping of an n-type polymer in vacuum has proven to be ineffi cient due to large scale phase segregation. [ 6 ] A more direct, molecular design approach of the side chains of a small molecule has shown potential, [ 5 ] exhibiting good performance inside a glovebox. Another promising n-type material are CNTs, which are intrinsically ambipolar when protected from air, and have been shown to work as both p-type and n-type thermoelectric materials.…”

“…0.01 µW m −1 K −2 for this work). [ 5,6 ] Since the presented method is likely to be applicable to other materials systems, we expect that signifi cantly higher effi ciencies can be reached by selecting better performing materials like semiconducting single-walled carbon nanotubes, and appropriate dopants, [ 53 ] while keeping processing complexity low by depositing a minimum number of layers and selecting a suitable transformation step like the UV-irradiation presented here, or other simple methods, like vapor printing. [ 54 ] Besides performance, stability is also a key parameter since most reported n-type organic materials are not stable in air.…”