Abstract:Improving the electrical conductivity is an important role in realizing high thermoelectric performance of solutionprocessable polymers. Herein, a simple and robust approach to boost the mobility and doping efficiency of a diketopyrrolopyrrolebased copolymer with the introduction of thermocleavable side chains (PDPPS-X, where X is the molar ratio of the thermocleavable side chains and alkyl chains) is first provided. Notably, the incorporated thermocleavable groups can be effectively removed after thermal trea… Show more
“…Meanwhile, the relationship of σ and S agrees well with Chabinyc’s empirical modeling for the D–A CPs that the absolute value of S decreased (increased) and σ increased (decreased) when their S changed its sign. According to the published papers, ,, the DPP-based D–A CPs were endowed by the DPP unit with semicrystalline properties that the strong molecular ordering requires a high doping concentration and a long doping time to be overdoped. Hence, the doped D–A CPs show almost little impact on the relationship of σ and S .…”
Section: Resultsmentioning
confidence: 99%
“…The three D−A CPs showed nearly the same FT-IR with the obvious characteristic bands at 1656 cm −1 (Figure S3b), which might be ascribed to the C�O stretching vibration in the DPP unit. 33,40,41 2.2. Polarity Switching.…”
Section: Synthesis and Characterization The Idt-based D−d-and D−a-typementioning
confidence: 99%
“…Herein, we report the expedited polarity switching process of IDT-based CPs through embedding conjugated phenyl groups in the side chain (BIDT) and extending the π-delocalization (BIDTT) of the IDT unit (Scheme ), which have been previously reported to endow the CPs with polarity switching. , The three IDT monomers (IDT, BIDT, and BIDTT) polymerized with 3.3″-dioctyl-2,2′:5′,2″-terthiophene unit (3T) and diketopyrrolopyrrole unit (DPP), respectively, forming three D–D CPs (PIDT-3T, PBIDT-3T, and PBIDTT-3T) and three D–A CPs (PIDT-DPP, PBIDT-DPP, and PBIDTT-DPP). The extended thiophene units (3T) on the D–D CP backbones could contribute to the high doping efficiency and favorable crystalline morphology, benefiting effective charge carrier transport. , The DPP unit could endow the D–A CPs with enhanced planarity and strong intermolecular interactions, leading to high hole mobilities and electron mobilities. − Therefore, the six IDT-based CPs were selected and synthesized for a thorough analysis of the polarity switching structure–function relationships.…”
Endowing a single conjugated polymer possessing high bipolar (both P-and N-types) electrical conductivities offers a considerable strategy to boost thermoelectric module performances. However, the effect of polymer structures on expediting the polarity switching process is rarely reported. Six indaceno [1,2b:5,6-b′]dithiophene(IDT)-based polymers (PIDT-3T, PBIDT-3T, PBIDTT-3T, PIDT-DPP, PBIDT-DPP, and PBIDTT-DPP) were synthesized by modifying the IDT unit through embedding phenyl groups in the side chain (BIDT) and extending the πdelocalization of backbones (BIDTT). After doping with FeCl 3 , all the six IDT-based CPs display a switch in the sign of the Seebeck coefficient. According to ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy, the polarity switching can be attributed to both the crossing of the Femi level from above transporting level to below transporting level and transport gap diminishment. The UV−vis absorption spectra and X-ray diffraction patterns demonstrated that the conjugated phenyl groups endow the BIDTT-based CPs with sufficient space along the polymer backbones for FeCl 3 distribution, and the extended backbones can promote the doping efficiency, accelerating the polarity switching process. Consequently, PBIDTT-DPP required the shortest polarity switching time of 1 min among the six polymers. This work provides an in-depth understanding of the polarity switching structure−function relationships and sheds light on the design of efficient n-type thermoelectric polymers.
“…Meanwhile, the relationship of σ and S agrees well with Chabinyc’s empirical modeling for the D–A CPs that the absolute value of S decreased (increased) and σ increased (decreased) when their S changed its sign. According to the published papers, ,, the DPP-based D–A CPs were endowed by the DPP unit with semicrystalline properties that the strong molecular ordering requires a high doping concentration and a long doping time to be overdoped. Hence, the doped D–A CPs show almost little impact on the relationship of σ and S .…”
Section: Resultsmentioning
confidence: 99%
“…The three D−A CPs showed nearly the same FT-IR with the obvious characteristic bands at 1656 cm −1 (Figure S3b), which might be ascribed to the C�O stretching vibration in the DPP unit. 33,40,41 2.2. Polarity Switching.…”
Section: Synthesis and Characterization The Idt-based D−d-and D−a-typementioning
confidence: 99%
“…Herein, we report the expedited polarity switching process of IDT-based CPs through embedding conjugated phenyl groups in the side chain (BIDT) and extending the π-delocalization (BIDTT) of the IDT unit (Scheme ), which have been previously reported to endow the CPs with polarity switching. , The three IDT monomers (IDT, BIDT, and BIDTT) polymerized with 3.3″-dioctyl-2,2′:5′,2″-terthiophene unit (3T) and diketopyrrolopyrrole unit (DPP), respectively, forming three D–D CPs (PIDT-3T, PBIDT-3T, and PBIDTT-3T) and three D–A CPs (PIDT-DPP, PBIDT-DPP, and PBIDTT-DPP). The extended thiophene units (3T) on the D–D CP backbones could contribute to the high doping efficiency and favorable crystalline morphology, benefiting effective charge carrier transport. , The DPP unit could endow the D–A CPs with enhanced planarity and strong intermolecular interactions, leading to high hole mobilities and electron mobilities. − Therefore, the six IDT-based CPs were selected and synthesized for a thorough analysis of the polarity switching structure–function relationships.…”
Endowing a single conjugated polymer possessing high bipolar (both P-and N-types) electrical conductivities offers a considerable strategy to boost thermoelectric module performances. However, the effect of polymer structures on expediting the polarity switching process is rarely reported. Six indaceno [1,2b:5,6-b′]dithiophene(IDT)-based polymers (PIDT-3T, PBIDT-3T, PBIDTT-3T, PIDT-DPP, PBIDT-DPP, and PBIDTT-DPP) were synthesized by modifying the IDT unit through embedding phenyl groups in the side chain (BIDT) and extending the πdelocalization of backbones (BIDTT). After doping with FeCl 3 , all the six IDT-based CPs display a switch in the sign of the Seebeck coefficient. According to ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy, the polarity switching can be attributed to both the crossing of the Femi level from above transporting level to below transporting level and transport gap diminishment. The UV−vis absorption spectra and X-ray diffraction patterns demonstrated that the conjugated phenyl groups endow the BIDTT-based CPs with sufficient space along the polymer backbones for FeCl 3 distribution, and the extended backbones can promote the doping efficiency, accelerating the polarity switching process. Consequently, PBIDTT-DPP required the shortest polarity switching time of 1 min among the six polymers. This work provides an in-depth understanding of the polarity switching structure−function relationships and sheds light on the design of efficient n-type thermoelectric polymers.
“…Summary of the best-performing p- and n-type polymeric TE materials in literature. p-Type: D−π, − ,,,,,,,,− ,− A−π, − and D–A − ,,− structures. n-Type: A–A, ,,,,,,, A−π, − ,,,,− ,,− and D–A ,,,,,,,, structures.…”
Section: Correlating Polymeric Structures With Electrical Characteris...mentioning
Thermoelectric (TE) materials can realize the direct
transformation
between heat and electricity, thereby facilitating the recycling of
waste heat. Semiconducting π-conjugated polymers (π-CPs)
have been largely explored as organic TE materials thanks to the facile
molecular tunability of their electronic properties, their room-temperature
solution-processability, their intrinsic low thermal conductivity,
and their outstanding mechanical flexibility. In this Focus Review,
we describe two key strategieschemical doping and structural
tailoringin polymeric TEs for strengthening TE power factors
of π-CPs. First, the doping mechanisms are unraveled by a sequential
process of charge transfer and free carrier release, followed by the
introduction of various doping methods for enhancing the chemical
doping. Second, the design principles for polymeric structures including
the π-backbone and side-chain engineering are presented. Third,
supplementary strategies such as polymer chain alignment and construction
of polymer blends are identified. Finally, the existing prime obstacles
to future development are discussed and an outlook on feasible solutions
to resolving them is provided.
“…Generally, organic molecules exhibit low σ. Chemical doping is an effective way to improve the σ value, and a lot of doped OTEMs have been developed with high performance. − For example, the performance of p-type doped poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT/PSS) has been greatly improved, and the ZT of which has reached 0.42 . In addition, combination with inorganic fillers is also a good way to improve the conductivity, among which, single-walled carbon nanotubes (SWCNTs) have been regarded as one of the best ones. − The pristine SWCNTs show p-type characteristics because of oxygen doping during the preparation and application process, nevertheless, high k and low performance limit their application.…”
Many drugs, foods, and clothes are derived from natural
products;
however, little attention has been focused on natural-derived thermoelectric
(TE) materials. In this work, several natural amino acids are first
introduced to single-walled carbon nanotubes (SWCNTs) and a series
of environment-friendly n- and p-type freestanding SWCNT/amino acid
films are fabricated as potent TE materials. Among the composites,
SWCNT/histidine (His) and SWCNT/lysine (Lys) achieve excellent n-type
TE properties, with the highest power factors of 508.5 and 502.0 μW
m–1 K–2 at room temperature, respectively.
SWCNT/aspartic acid (Asp) displays p-type behaviors, with the highest
power factor of 221.6 μW m–1 K–2 at room temperature. Moreover, a TE device based on SWCNT/Lys and
SWCNT/Asp including five p–n junctions is fabricated. The high
open-circuit voltage (42.3 mV) and output power (4.3 μW) are
obtained at ΔT = 87 K. Given the excellent
TE performance, green composites based on natural-derived materials
can be the promising candidates for TE devices.
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