N-type Polymer Research Articles

Screening of Different Carbon Nanotubes in Melt-Mixed Polymer Composites with Different Polymer Matrices for Their Thermoelectrical Properties

The aim of this study is to reveal the influences of carbon nanotube (CNT) and polymer type as well as CNT content on electrical conductivity, Seebeck coefficient (S), and the resulting power factor (PF) and figure of merit (ZT). Different commercially available and laboratory made CNTs were used to prepare melt-mixed composites on a small scale. CNTs typically lead to p-type composites with positive S-values. This was found for the two types of multi-walled CNTs (MWCNT) whereby higher Seebeck coefficient in the corresponding buckypapers resulted in higher values also in the composites. Nitrogen doped MWCNTs resulted in negative S-values in the buckypapers as well as in the polymer composites. When using single-walled CNTs (SWCNTs) with a positive S-value in the buckypapers, positive (polypropylene (PP), polycarbonate (PC), poly (vinylidene fluoride) (PVDF), and poly(butylene terephthalate) (PBT)) or negative (polyamide 66 (PA66), polyamide 6 (PA6), partially aromatic polyamide (PARA), acrylonitrile butadiene styrene (ABS)) S-values were obtained depending on the matrix polymer and SWCNT type. The study shows that the direct production of n-type melt-mixed polymer composites from p-type commercial SWCNTs with relatively high Seebeck coefficients is possible. The highest Seebeck coefficients obtained in this study were 66.4 µV/K (PBT/7 wt % SWCNT Tuball) and −57.1 µV/K (ABS/0.5 wt % SWCNT Tuball) for p- and n-type composites, respectively. The highest power factor and ZT of 0.28 µW/m·K2 and 3.1 × 10−4, respectively, were achieved in PBT with 4 wt % SWCNT Tuball.

N-type conjugated polymer as efficient electron transport layer for planar inverted perovskite solar cells with power conversion efficiency of 20.86%

Fullerene and its derivatives are commonly used as electron transport layers (ETLs) in inverted perovskite solar cells (PSCs), since they show suitable band alignment and good electron mobility. However, fullerene-based ETLs typically result in low open-circuit voltages due to the interfacial defects, and they also exhibit poor photochemical and thermal stability. Consequently, there is great interest in the development of novel ETLs for high-performance inverted PSCs. In this work, two n-type polymers PBTI and PDTzTI are utilized as ETL in inverted PSCs, which are based on bithiophene imide and thienylthiazole imide, respectively. Due to its high electron mobility, well matched energy level alignment together with the passivation of interfacial traps/defects, device with the PDTzTI ETL demonstrates a best power conversion efficiency of 20.86%, which outperform those with PBTI and PCBM ETLs. Owning to the highly hydrophobic properties as well as the mobile ion blocking capability of polymer, PDTzTI ETL based device also exhibits excellent long-term and operational device stability as compared with the PCBM one. Our results demonstrate that rational selection of ETLs has great impact on the device efficiency and stability in inverted planar PSCs and that novel n-type polymer might be ideal alternative ETL in inverted planar PSCs.

The effect of alkyl chain branching positions on the electron mobility and photovoltaic performance of naphthodithiophene diimide (NDTI)-based polymers

Conjugated polymers are widely used in organic optoelectronic devices due to their solution processability, thermal stability and structural diversity. Generally, alkyl side chains must be utilized to increase the solubility of final polymers in the processing solvent. However, the effects of different type alkyl chains on the properties of n-type photovoltaic polymers have rarely been investigated. In this article, we synthesized three naphthodithiophene diimide (NDTI) based polymers containing bulky alkyl chains with different branching position, named as NDTI-1, NDTI-2 and NDTI-3, respectively. We systematically investigated the effect of different branching point on the molecular packing, charge transport and photovoltaic performance. When moving the branching point away from the backbone, the intermolecular interaction became stronger, which could be proved by 2D grazing incidence wide angle X-ray scattering (GIWAXS) measurement. Therefore, the electron mobilities in organic field-effect transistors gradually increased from 2.11×10−3 cm2 V−1 s−1 for NDTI-1 to 4.70×10−2 cm2 V−1 s−1 for NDTI-2 and 9.27×10−2 cm2 V−1 s−1 for NDTI-3, which are quite high values for polymers with face-on orientation. In addition, the NDTI-2 and NDTI-3 thin films exhibited red-shifted absorption spectra compared with NDTI-1. When blending with three classic donor polymers PBDB-T, PTB7-Th and PE61, NDTI-2 based devices always showed the higher power conversion efficiencies (PCEs) than the other two polymers (beside the comparable result of PTB7-Th:NDTI-3 combination) as a result of the high photocurrent response and high fill factor. Our results indicate that bulky alkyl chain with branching point at 2-position should be a good and safe choice for the design of naphthodithiophene diimide-based and even naphthalene diimide-based n-type photovoltaic polymers.

Fused Bithiophene Imide Oligomer and Diketopyrrolopyrrole Copolymers for n-Type Thin-Film Transistors.

Diketopyrrolopyrrole (DPP)-based copolymers have received considerable attention as promising semiconducting materials for high-performance organic thin-film transistors (OTFTs). However, these polymers typically exhibit p-type or ambipolar charge-transporting characteristics in OTFTs due to their high-lying highest occupied molecular orbital (HOMO) energy levels. In this work, a new series of DPP-based n-type polymers have been developed by incorporating fused bithiophene imide oligomers (BTIn) into DPP polymers. The resulting copolymers BTIn-DPP show narrow band gaps as low as 1.27 eV and gradually down-shifted frontier molecular orbital energy levels upon the increment of imide group number. Benefiting from the coplanar backbone conformation, well-delocalized π-system, and favorable polymer chain packing, the optimal polymer in the series shows promising n-type charge transport with an electron mobility up to 0.48 cm2 V-1 s-1 in OTFTs, which is among the highest values for the DPP-based n-type polymers reported to date. The results demonstrate that incorporating fused bithiophene imide oligomers into polymers can serve as a promising strategy for constructing high-performance n-type polymeric semiconductors.

Exploring a Fused 2-(Thiophen-2-yl)thieno[3,2-b]thiophene (T-TT) Building Block to Construct n-Type Polymer for High-Performance All-Polymer Solar Cells.

In the field of all-polymer solar cells, exploring new electron-donating units (D) to match with electron-accepting units (A) is an important subject to promote the performance of D-A-type polymer acceptors. Herein, we developed a fused D unit 2-(thiophen-2-yl)thieno[3,2-b]thiophene (T-TT) derivated from the famous 2-(2-(thiophen-2-yl)vinyl)thiophene (TVT) unit. With classical naphthalene diimide (NDI) as A unit, the new D-A polymer PNDI-T-TT exhibits enhanced absorption coefficient, electron mobility, and miscibility with donor polymer in comparison with the analogous PNDI-TVT polymer. These advantages can be attributed to the enlarged conjugation and reduced rotamers due to the fused T-TT unit, leading to a stronger intermolecular interaction. When blending with the donor polymer PBDB-T, both NDI-based polymers can form better interpenetrating nanostructures than the corresponding blend films with the donor polymer J71. Finally, PBDB-T/PNDI-T-TT device achieves a power conversion efficiency of 6.1%, which is much higher than that of PBDB-T/PNDI-TVT device (4.24%). These results demonstrate that n-type polymer based on fused T-TT unit can ameliorate the absorption coefficient, molecular aggregation, and charge-carrier mobility and consequently achieve an improved photovoltaic performance in comparison with the classic TVT unit.

A Narrow‐Bandgap n‐Type Polymer Semiconductor Enabling Efficient All‐Polymer Solar Cells

Currently, n-type acceptors in high-performance all-polymer solar cells (all-PSCs) are dominated by imide-functionalized polymers, which typically show medium bandgap. Herein, a novel narrow-bandgap polymer, poly(5,6-dicyano-2,1,3-benzothiadiazole-alt-indacenodithiophene) (DCNBT-IDT), based on dicyanobenzothiadiazole without an imide group is reported. The strong electron-withdrawing cyano functionality enables DCNBT-IDT with n-type character and, more importantly, alleviates the steric hindrance associated with typical imide groups. Compared to the benchmark poly(naphthalene diimide-alt-bithiophene) (N2200), DCNBT-IDT shows a narrower bandgap (1.43 eV) with a much higher absorption coefficient (6.15 × 104 cm-1 ). Such properties are elusive for polymer acceptors to date, eradicating the drawbacks inherited in N2200 and other high-performance polymer acceptors. When blended with a wide-bandgap polymer donor, the DCNBT-IDT-based all-PSCs achieve a remarkable power conversion efficiency of 8.32% with a small energy loss of 0.53 eV and a photoresponse of up to 870 nm. Such efficiency greatly outperforms those of N2200 (6.13%) and the naphthalene diimide (NDI)-based analog NDI-IDT (2.19%). This work breaks the long-standing bottlenecks limiting materials innovation of n-type polymers, which paves a new avenue for developing polymer acceptors with improved optoelectronic properties and heralds a brighter future of all-PSCs.

Fluorine-Substituted Dithienylbenzodiimide-Based n-Type Polymer Semiconductors for Organic Thin-Film Transistors.

Imide functionalization is one of the most effective approaches to develop electron-deficient building blocks for constructing n-type organic semiconductors. Driven by the attractive properties of imide-functionalized dithienylbenzodiimide (TBDI) and the promising device performance of TBDI-based polymers, a novel acceptor with increased electron affinity, fluorinated dithienylbenzodiimide (TFBDI), was designed with the hydrogen replaced by fluorine on the benzene core, and the synthetic challenges associated with this highly electron-deficient fluorinated imide building block are successfully overcome. TFBDI showed suppressed frontier molecular orbital energy levels as compared with TBDI. Copolymerizing this new electron-withdrawing TBDI with various donor co-units afforded a series of n-type polymer semiconductors TFBDI-T, TFBDI-Se, and TFBDI-BSe. All these TFBDI-based polymers exhibited a lower-lying lowest unoccupied molecular orbital (LUMO) energy level than the polymer analogue without fluorine. When applied in organic thin-film transistors, three polymers showed unipolar electron transport with large on-current/off-current ratios (Ion/Ioff) of 105-107. Among them, the selenophene-based polymer TFBDI-Se with the deepest-positioned LUMO and optimal chain stacking exhibited the highest electron mobility of 0.30 cm2 V-1 s-1. This result demonstrates that the new TFBDI is a highly attractive electron-deficient unit for enabling n-type polymer semiconductors, and the fluorination of imide-functionalized arenes offers an effective approach to develop more electron-deficient building blocks in organic electronics.

Recent Progress in All-Polymer Solar Cells Based on Wide-Bandgap p-Type Polymers.

All-polymer solar cells (all-PSCs), with the photoactive layer exclusively composed of polymers as both donor and acceptor, have attracted growing attention due to their unique merits in optical, thermal and mechanical durability. Through the combined strategies in materials design and device engineering, recently the power conversion efficiencies of single-junction all-PSCs have been boosted up to 11 %. This review focuses on the recent progress of all-PSCs comprising of wide band-gap p-type polymers, especially those based on the units of thieno[3,4-c]pyrrole-4,6(5H)-dione], fluorinated benzotriazole, benzo[1,2-c:4,5-c']dithiophene-4,8-dione, and pyrrolo[3,4-f]benzotriazole-5,7(6H)-dione. Meantime, several categories of n-type polymers used to match with these polymer donors are also reviewed. Finally, a brief summary of the strategies of molecular design and morphology optimization is given, and strategies toward further improving performance of all-PSCs are outlined.

Thermoelectric polymer composite yarns and an energy harvesting wearable textile

A thermoelectric wearable is proposed based on an innovative 3D wearable design, with p- type polymer impregnated cotton yarns and n-type polymer impregnated cotton yarns, where the ratio of the p-/n-type yarn cross-sections is optimised to maximise the thermoelectric conversion efficiency. The thermoelectric yarns are embroidered through a double-layer cotton fabric, using plain-stitch, and connected via painted silver electrodag patches. The first stage of this study involved the characterisation of P3HT-, PEDOT:PSS- and PCBM-cotton fabric composite samples, in terms of their fibre volume fraction, specific heat capacity, thermal conductivity, electrical conductivity, Seebeck coefficient, Z and power factors. In this initial assessment, P3HT was selected as the p-type polymer compared to PEDOT:PSS, and PCBM was selected as the n-type polymer. A small, 3D wearable prototype was fabricated and tested: it exhibited a Seebeck coefficient of 380 μV K−1 but a relatively high resistance. It was estimated that scaling up this thermoelectric wearable to body coverage would produce about 1.5–2 μW for a temperature difference of 40 °C applied on the thermoelectric device.

Asymmetric Aqueous Supercapacitor Based on p- and n-Type Conducting Polymers

We demonstrated an asymmetric aqueous supercapacitor made of p- and n-type conducting polymer electrodes. We used the high electron affinity (EA) n-type polymer poly(benzimidazobenzophenanthroline)...

Rigid Coplanar Polymers for Stable n-Type Polymer Thermoelectrics.

Low n-doping efficiency and inferior stability restrict the thermoelectric performance of n-type conjugated polymers, making their performance lag far behind of their p-type counterparts. Reported here are two rigid coplanar poly(p-phenylene vinylene) (PPV) derivatives, LPPV-1 and LPPV-2, which show nearly torsion-free backbones. The fused electron-deficient rigid structures endow the derivatives with less conformational disorder and low-lying lowest unoccupied molecular orbital (LUMO) levels, down to -4.49 eV. After doping, two polymers exhibited high n-doping efficiency and significantly improved air stability. LPPV-1 exhibited a high conductivity of up to 1.1 S cm-1 and a power factor as high as 1.96 μW m-1 K-2 . Importantly, the power factor of the doped LPPV-1 thick film degraded only 2 % after 7 day exposure to air. This work demonstrates a new strategy for designing conjugated polymers, with planar backbones and low LUMO levels, towards high-performance and potentially air-stable n-type polymer thermoelectrics.

Strategies To Enhance the Conductivity of n-Type Polymer Thermoelectric Materials

In the past several decades, conducting polymers have achieved remarkable progress and have been widely applied as the active materials for optoelectronics. So far, p-type conducting polymers exhibit high conductivities over 1000 S cm–1 and thermoelectric performance comparable to that of inorganic materials; however, only a few n-type conducting polymers showed conductivities over 1 S cm–1 after doping. The low conductivity of n-type conducting polymers is considered as the major barrier for further enhancing their thermoelectric performances. In this perspective, we highlight the scientific and engineering challenges to enhance the conductivity of n-type polymer thermoelectric materials, including n-doping efficiency in n-type polymers, factors influencing charge carrier mobilities after doping, and stability of n-type conducting polymers. Recent development and strategies to address these issues and enhance the conductivity of n-type conjugated polymers are summarized and discussed, providing materials...

Azadipyrromethene-based near-IR dyes with styryl substituents at the pyrrolic positions for organic photovoltaic applications

Azadipyrromethene dyes are attractive building blocks for the development of near-IR dyes, with applications ranging from biosensing, photodynamic therapy and solar energy conversion. In particular, Zn(II) bis(2,8-diphenylethynyl 1,3,7,9 tetraphenylazadipyrromethene) complexes are promising n-type non-fullerene electron acceptors for organic photovoltaics. Here, the triple bond in phenylethynyl pyrrolic substituents is replaced with a double bond. The UV–Vis absorption spectra were not significantly different, indicating that both the double and triple bond similarly extend the conjugation of ADP. Interestingly, the Zn(II) complex with styryl substituents (Zn(WS6)2) showed emission in the near IR, with a λmax of 773 nm. The BF2+ chelate also emitted in the near IR with a λmax of 815 nm, but the emission was very weak. Cyclic voltammetry revealed that double bond compounds were easier to oxidize than un-substituted ADP analogues, and unlike with triple bond, were not easier to reduce. In organic photovoltaics, the Zn(WS6)2 did not perform as well as the Zn(WS3)2 analogue, showing unfavorable film morphology when blended with P3HT and low blend electron mobility of 2 × 10−8 cm2V−1s−1 by SCLC, compared to 1 × 10−7 cm2V−1s−1 in neat film. The hole mobility of Zn(WS6)2 in neat films is 6 × 10−5 cm2V−1s−1, higher than its electron mobility, suggesting its potential as p-type material as well. Further work in finding an appropriate n-type polymer acceptor is required to confirm this hypothesis. Using a triple bond at the pyrrolic positions is therefore better than a double bond for the development of n-type materials based on ADP dyes.

Improved Electron Injection and Transport in Semiconducting Polymers By Doping with Guanidino-Functionalized Aromatic Compounds

Efficient and stable n-dopants are still rare but highly desired for organic electronics and thermoelectrics. Many high mobility, n-type semiconducting polymers still show some hole transport, which is unwanted for applications in complementary inverters, as it gives rise to increased power dissipation. The use of n-type contact dopants that block the injection of holes is thus beneficial. We successfully applied 1,2,4,5-tetrakis(tetramethylguanidino)benzene (ttmgb), a guanidino-functionalized aromatic (GFA) compound, as a strong two-electron donor to networks of single-walled carbon nanotube field-effect transistors to create purely n-type devices with high electron mobilities and high on/off current ratios [1]. Here, we demonstrate the versatility of this dopant by applying it to the well-known n-type (but still slightly ambipolar) polymer semiconductor P(NDI2OD-T2).The dopant ttmgb can be processed directly from solution, which leads to significantly improved device characteristics. Additionally, we show that vapor deposition of ttmgb is another pathway to high-performance injection layers. In all cases, the injection of electrons and their mobility is significantly improved compared to the untreated reference samples. In addition, the injection of holes is blocked by ttmgb2+ on the electrode surface, which enables the fabrication of solely n-type FETs. Contact doping with ttmgb and other GFAs could potentially also be used on other semiconducting materials, e.g. for two-dimensional transition metal dichalcogenides, and may find widespread application in high performance thin film electronics. [1] Schneider et al., ACS Nano 2018, 12 (6), 5895-5902 Figure 1

(Invited) Emerging Designs for Polymer-Based Energy Storage Devices and Sensors

Conducting polymers are an important class of Faradaic materials for energy storage, as they present opportunities to create energy dense supercapacitors. The vast majority of conducting polymers are p-type cathodes and already operating at or close to the upper voltage limit of non-aqueous electrolytes. On the other hand, it is generally safe for electrolytes to operate down to -2 V vs Standard Hydrogen Electrode. Therefore, extending the operational voltage in the negative range is an attractive route to increase energy density. Here we present promising n-type polymers that retained 90% of initial capacitance after 1000 charge-discharge cycles. We measure in operando the electronic and ionic transport in conducting polymers by current-voltage and spectroscopic measurements, where spatial variations of film absorption would be mapped to discern electronic versus ionic degradation. We infer the mechanisms that lead to capacitance fade and suggests structural and electrochemical strategies to realize high-endurance energy storage devices for wearable systems. In addition, organic polymers responsive to the short wavelength infrared (SWIR) spectra are used to realize photodetectors that is relevant to a variety of applications including environmental monitoring and medical diagnosis. Here we show novel donor-acceptor polymers with narrow bandgap responsive in the SWIR region, and the polymers are processed into bulk heterojunction photodiodes with photoresponse up to wavelength of 1.7 micron. The performances of devices with different polymer structures were compared through metrics including detectivity, quantum efficiency, response time and rectification ratio. Example applications including hemodynamics and tissue composition measurements will be demonstrated.

From Isotropic to Anisotropic Conductivities in P(NDI2OD-T2) by (Electro-)Chemical Doping Strategies

Both electrochemical and chemical doping of the n-type regioregular polymer poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)) and its regioirregular counterparts are presented. Electrochemical doping clearly shows that a 2-fold reduction with maximum conductivity in the radical-anion state is possible with the polymers. Chemical doping with the state-of-the-art high-performance dopants 4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzeneamine (N-DMBI) and tetrakis(dimethylamino)ethylene (TDAE) gives conductivity values between 10–4 and 10–3 S cm–1 for as-cast films with clear involvement of the radical-anion species. Anisotropic conductivities of vapor-doped blade-coated films give up to 6 times higher values along the polymer chain direction compared with the perpendicular direction, both in face-on and edge-on oriented chains in the bulk of the films. The polymorph concomitantly changes from a mixed stacking of na...

Body Heat Powers Future Electronic Skins

Ruoming Tian recently joined the Mark Wainwright Analytical Centre as an XRD research assistant at the University of New South Wales. She was formerly a Research Scientist at the Toyota Physical and Chemical Research Institute in Japan (2015–2018) and received her PhD from the University of New South Wales in 2014. Her research interests focus on the nano- and micro-materials, flexible hybrid materials, and smart devices for harvesting both high- and low-grade thermal energy. She has published 2 book chapters and 18 peer-reviewed articles and delivered more than 15 talks at international conferences and leading research institutes. Yuqing Liu is currently an Associate Research Fellow and received her PhD (2018) in the Intelligent Polymer Research Institute (IPRI), University of Wollongong, Australia. Her research interest is on the fabrication of wearable energy storage and conversion devices (e.g. thermos-cells, batteries, supercapacitors, etc.), mainly focusing on nanostructured electrode materials, gel electrolyte/electrode interface, and device fabrication via printing techniques. Kunihito Koumoto, Professor Emeritus of Nagoya University, received his BS, MS, and PhD from the University of Tokyo (UT). He served as an Assistant Professor, Lecturer, and Associate Professor at UT (1979–1992) and a full professor at Nagoya University (1992–2015). He has published 495 papers and reviews and 58 book chapters in inorganic materials chemistry. He was awarded Medal with Purple Ribbon by the Emperor of Japan in 2013 and Outstanding Achievement Award by the International Thermoelectric Society in 2018. His current research focuses on inorganic/organic nanohybrid thermoelectrics for energy harvesting. Koumoto can be reached by email at koumoto@apchem.nagoya-u.ac.jp . Jun Chen is currently a Full Professor at IPRI|ACES, Australian Institute for Innovative Materials, University of Wollongong (UOW). He received BE from Zhejiang University of Technology (1995) and PhD from UOW (2003). Professor Chen has published more than 180 papers and has been named a Highly Cited Researcher for 2018 (Clarivate Analytics). His research interests include sustainable energy devices, electro-/bio-interfaces, nano-/micro-materials, 2D/3D printing, and smart wearable electronic devices. Apart from academic achievements, Chen has also been involved in two spin-off companies: AQUAHYDREX as one of the key inventors, and IMAGINE as one of the scientific founders.

Poly(fluorene-alt-naphthalene diimide) as n-Type Polymer Electrodes for Energy Storage

Redox-active polymers, especially conjugated polymers, are of interest for use in battery electrodes due to their conductivity, synthetic versatility, and processability. Conjugated polymers store ...

Effect of Thionation on the Performance of PNDIT2-Based Polymer Solar Cells

All-polymer solar cells have gained attention in recent years with a solar cell performance of over 11% power conversion efficiency (PCE) recently demonstrated. The n-type polymer PNDIT2, also known as N2200 or P(NDI2OD-T2), has been extensively used for both photovoltaic and field-effect transistor applications. When paired with donor materials that have appropriately aligned energy levels, PNDIT2 exhibited device efficiencies over 10% PCE, and organic field-effect transistors fabricated with PNDIT2 exhibited mobilities over 1 cm2/V s. Thionation of the naphthalene diimide (NDI) moiety, which is the substitution of imide oxygen with sulfur atoms, has been shown to improve the field-effect transistor performance of NDI-based small molecules. By applying this strategy to PNDIT2, we explored the effect that thionation, in a 2S-trans configuration, has on the performance of all-polymer solar cells fabricated with the donor polymer PTB7-Th. Solar cells were fabricated with the original polymer, PNDIT2, as a r...

Thermoelectric Performance of n‐Type Poly(Ni‐tetrathiooxalate) as a Counterpart to Poly(Ni‐ethenetetrathiolate): NiTTO versus NiETT

AbstractThe synthesis of the metal‐coordination polymer poly(nickel tetrathiooxalate) (NiTTO) is presented, which represents an alternative route to n‐type thermoelectric materials similar in nature to nickel ethenetetrathiolate (NiETT) polymers. The TTO monomer is synthesized through an electrochemical reduction of carbon disulfide, followed by coordination polymerization with a nickel(II) salt to yield a coordination complex polymer with a neutral repeat unit. An alkali metal counterion exchange and polymerization optimization are performed, and a thermoelectric power factor of 6 µW m−1 K−2 (electrical conductivity of over 10 S cm−1) is achieved for NiTTO composite films in a polyvinylidene fluoride (PVDF) matrix. This is significantly higher than other reported n‐type polymers (and to within a factor of two of NiETT) and demonstrates the potential of NiTTO as a new thermoelectric material. Elemental analysis indicates a nearly neutral backbone structure in NiTTO with minimal charge balancing alkali ions, indicating that these polymers are more oxidized than NiETTs. X‐ray photoelectron spectroscopy reveals a different coordination environment for NiTTO compared to NiETTs with the same alkali counterion, indicating that—despite their structural similarity in theory—these two materials are indeed different.