ABSTRACT Conjugated polymers are promising thermoelectric materials offering solution processability, flexibility, and versatile synthesis. However, n‐type polymers lag behind their p‐type counterparts. Herein, we demonstrate that the combination of precise doping with control over crystalline contact plane, orientation, and microstructure helps design efficient n‐type films of a naphthalenediimide‐bithiazole‐based copolymer (PNDIOE7‐Tz2). Favorable fibrillar morphology and enhanced planarity lead to tight packing in films doped with N‐DMBI, resulting in a high electrical conductivity σ ≈ 10 S cm −1 . GIWAXS indicates a predominantly face‐on orientation in pristine films with a short π–π stacking distance of 3.47 Å. Incremental concentration doping enhances the σ to 45 S cm −1 with a power factor (PF≈17.5 µW m −1 K −2 ). Rubbing alignment causes a detrimental shift from face‐on to edge‐on, reducing σ below 5 S cm −1 and PF below 4 µW m −1 K −2 . Subsequent solvent vapor annealing converts aligned crystallites to mixed face‐on/edge‐on, promoting a strong enhancement of TE performance with a high PF up to 41µW m −1 K −2 , among the highest reported for n‐type polymers. This work underscores that controlling the contact plane effectively decouples σ and S for high‐performance n‐type polymer thermoelectrics.

This study demonstrates the possibility to enhance thermoelectric properties of n‐type benzodifuranone‐based copolymers using a combination of polymer orientation (using high temperature rubbing) and sequential doping with the dopant N‐DMBI‐H. It focuses on the impact of the side chain length and the chemical nature of the comonomer (thiophene vs furan) on the efficacy of this methodology that preserves the facile solution‐processability of this polymer family and enables effective sequential doping without a thermal activation step. The combination of high temperature rubbing and thermal annealing helps reach a high orientation of the copolymers with the thiophene comonomer regardless of the length of the side chains whereas the furan‐based polymer is marginally aligned. The high orientation of thiophene‐based copolymers results in a strong improvement of electrical conductivity and power factors reaching up to 9.8 ± 1.6 S cm −1 and 8 ± 3 µW m −1. K 2 , respectively.

In this contribution, doping of oriented thin films is investigated for three PBTTT polymers bearing different side chains including linear alkyl & horbar;(CH2)12 & horbar;H, single ether & horbar;(CH2)7 & horbar;O & horbar;(CH2)4 & horbar;H and alkyl-siloxane & horbar;(CH2)5 & horbar;(Si(CH3)2O)2 & horbar;Si(CH3)3 A combination of transmission electron microscopy, polarized UV-vis-NIR spectroscopy and transport measurements helps uncover the essential role of the chemical nature of side chains on the efficacy of the doping and on the resulting thermoelectric performances in oriented PBTTT films. Siloxane side chains help to reach record alignment level of PBTTT with dichroic ratio beyond 50 for an optimized rubbing temperature but they impede effective doping of PBTTT crystals with F6TCNNQ, resulting in very poor TE properties. By contrast, doping the amorphous phase of all three PBTTTs with magic blue (MB) results in excellent TE performances. Both, chemical nature of side chains and semi-crystalline structure of the polymer determine the efficacy of doping. The use of siloxane side chains further impacts the scaling laws S proportional to sigma-1/s between the Seebeck coefficient S and the charge conductivity sigma. An unexpected s = 2 exponent is observed and tentatively attributed to the dimensionality of charge transport in the highly oriented mesophase of PBTTT.

The proliferation of distributed microelectronics and sensors necessitates adaptable, scalable, and cost-effective power supplies. Organic thermoelectric generators (TEGs) that promise to harness heat sustainably and cost-effectively are seen as pivotal elements in shaping future sensor infrastructures. Recent strides in morphological control through the alignment of conjugated polymer backbones have enhanced the thermoelectric performance of doped organic semiconductors to record values, matching expectations for real applications. However, the hurdles in crafting and deploying organic TEGs effectively exploiting aligned polymer films remain unexplored. This work presents a design and fabrication method to incorporate aligned films into a thin label-like TEG. Thin films of regioregular poly(3-hexylthiophene) (P3HT) and poly(2,5-bis((7-butoxyheptyl)thiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-8O) are aligned via high-temperature rubbing technique inducing a high degree of anisotropy in their charge transport properties. The crystal structure and anisotropy of the films are exploited to realize monolithic TEGs by patterning conductive thermoelements via local inkjet doping of films transferred on ultrathin parylene substrates. The TEGs based on aligned P3HT and PBTTT-8O exhibit exceptional TEG power factors of 0.33 and 1.04 nW cm-2 K-2, respectively. Lastly, as a proof-of-concept use case for the TEGs, a thermoelectrically-powered volume-indicating label is presented as a potential application in the healthcare and food industries.

Organic electrochemical transistors (OECTs) are central to the development of highly sensitive (bio)sensors, energy‐efficient neuromorphic devices, and high‐precision electrophysiological monitoring systems. With growing interest in these strategic electronic devices, a novel PBTTT polymer bearing single‐ether side chains ( PBTTT‐ 8 O ) in OECTs is investigated. Pristine isotropic non‐aligned OECT performance matches state‐of‐the‐art transconductance, highlighting the potential of single ethers for designing high‐performance organic mixed ionic‐electronic conductors (OMIECs). Moreover, a 13× enhancement of current output is achieved by anisotropic polymer chain alignment of PBTTT‐ 8 O , opening doors to unprecedented device sensitivity. Compared to pristine ones, aligned OECTs afford a 6× increase in the normalized transconductance (g m L/Wd), reaching an unprecedented 2 580 S cm −1 . Such improvement is mainly due to a gain in carrier mobility µ, as evidenced by four distinct methods. In addition, aligned OECTs exhibit faster doping front propagation, ON switching, and OFF switching compared to pristine ones. This study hence reports a versatile and easily transferable approach to concomitantly boost signal amplification and accelerate the response time of bioelectronic devices.

This study provides the first experimental polarized intermolecular and intramolecular optical absorption components of field-induced polarons in regioregular poly(3-hexylthiophene-2,5-diyl), rr-P3HT, a polymer semiconductor. Highly aligned rr-P3HT thin films were prepared by a high temperature shear-alignment process that orients polymer backbones along the shearing direction. rr-P3HT in-plane molecular orientation was measured by electron diffraction, and out-of-plane orientation was measured through series of synchrotron X-ray scattering techniques. Then, with molecular orientation quantified, polarized charge modulation spectroscopy was used to probe mid-IR polaron absorption in the ℏω = 0.075 - 0.75 eV range and unambiguously assign intermolecular and intramolecular optical absorption components of hole polarons in rr-P3HT. This data represents the first experimental quantification of these polarized components and allowed long-standing theoretical predictions to be compared to experimental results. The experimental data is discrepant with predictions of polaron absorption based on an adiabatic framework that works under the Born-Oppenheimer approximation, but the data is entirely consistent with a more recent nonadiabatic treatment of absorption based on a modified Holstein Hamiltonian. This nonadiabatic treatment was used to show that both intermolecular and intramolecular polaron coherence break down at length scales significantly smaller than estimated structural coherence in either direction. This strongly suggests that polaron delocalization is fundamentally limited by energetic disorder in rr-P3HT.

Single-ether side chains allow modulation of the oxygen position. The further the oxygen atom is from the backbone, the more crystalline the polymer. High doping levels and ordering lead to remarkable conductivities and thermoelectric performances.

This study focuses on the impact of dopant location in the semicrystalline structure of regioregular poly(3-hexylthiophene-2,5-diyl) on the long-term stability of thermoelectric properties probed in rub-aligned films. Phase-selective doping is possible by suitable choice of dopants. Anion exchange doping results in TFSI dopants located in both crystalline and amorphous domains whereas magic blue dopants are located in the amorphous phase only. The combination of rub-alignment, increasing concentration doping, and anion exchange doping is effective to produce doped P3HT films with enhanced thermoelectric properties and stability. Transmission electron microscopy, polarized optical absorption spectroscopy, and transport measurements help identify different regimes of doping: crystalline domains are doped first by exchange of F4TCNQ- with TFSI-, followed by a progressive doping of amorphous regions. The best thermoelectric performances of TFSI-exchanged P3HT lead to power factors in the 160-170 mu W m-1 K-2 range. Despite similar TE performances, MB-doped and TFSI-exchanged P3HT films behave very differently on aging. Numerically exact kinetic Monte Carlo simulations clarify the origin of this difference. The retention of charges in any phase is crucial for the stability in conductivity, but the conductivity at long aging times, sigma infinity is quantitatively determined by the specific phase retaining the charges. This study focuses on the impact of dopant location in the semicrystalline structure of poly(3-hexylthiophene) (P3HT) on the long-term stability of thermoelectric properties. Phase-selective doping is possible by a suitable choice of dopants. The retention of charges in any phase determines the stability in conductivity, but the conductivity at long aging times depends on the specific phase capable of retaining the charges. image

Photovoltaic spatial light modulators (PSLM) are self-activated optical devices that can be used as dynamic glazing or as optically addressable spatial light modulator. The range of potential applications of this new kind of optical device is highly dependent on its clear-state transmittance, spectral distribution of transmittance modulation, as well as on its response time, stability, and spatial resolution. These features are in turn mainly determined by the materials used for the various parts making up a PSLM, namely the photovoltaic unit, the liquid crystal layer, the liquid crystal alignment layers, and the polarizers. This contribution will focus on the multiple links between material properties and device performance and present our recent results on the design and processing of organic semiconductor materials designed to broaden the field of applications of PSLMs.

Understanding transport phenomena in conducting polymers (CP) is a main issue in order to optimize their performance and despite intense investigations, the influence of their microstructure remains controversial. By analyzing the thermoelectric measurements performed on highly oriented and non-oriented CP films, we show that an Heterogeneous Oriented Structure (HOSt) model considering both ordered and disordered domains is able to account for the thermoelectric transport in CP. This model unveils the key role of the crystallinity, the anisotropy and the alignment degree of these domains. It points out the importance of the thermal conductivity in the interpretation of the thermopower [Formula: see text] and explains the frequently observed electrical conductivity [Formula: see text] cut-off in the [Formula: see text] curves due to the disordered domains. By varying the alignment degree depending on the orientation and the anisotropy according to the face-on or the edge-on polymers conformation, the HOSt model successfully describes the overall measured thermoelectric properties by demonstrating its applicability to a wide variety of both oriented and non-oriented CP.

Alignment of conjugated polymerssuch as regioregularpoly(3-hexylthiophene-2,5-diyl)(rr-P3HT) is an effective means to enhance charge transport and thermoelectricproperties of thin films doped with F(4)TCNQ. In this contribution,we investigate the impact of P3HT regioregularity (RR) on the alignmentachieved in thin films by high-temperature rubbing and the resultingthermoelectric properties in sequentially doped and aligned films.The structure and thermoelectric properties of doped P3HT thin filmsare investigated by a combination of transmission electron microscopy(electron diffraction), polarized UV-vis-NIR spectroscopy,and thermoelectric measurements. Despite limited thermomechanicalproperties, rubbing at 165 & DEG;C generates order and alignment in71% RR P3HT (R71-P3HT) with a typical lamellar stacking of P3HT chainssimilar to that of the smectic-like phase of RR-P3HT. Order is furtherenhanced in aligned R71-P3HT films by doping with F(4)TCNQ.Intercalation of dopants in the ordered domains of R71-P3HT inducesa reorganization of polythiophene backbones within individual & pi;-stackswith lattice parameter variations equivalent to those observed forRR-P3HT. Despite ordering induced by both rubbing at 165 & DEG;C anddoping, charge conductivity of oriented R71-P3HT in the chain directionremains 50 times below that of oriented RR-P3HT. The strong blue-shiftof the polaronic bands in R71-P3HT versus RR-P3HT indicates that polaronsare strongly localized in both ordered and amorphous zones of R71-P3HT,explaining the modest charge conductivity of 3-4 S/cm observedin the chain direction.

The location of dopants in the crystalline and/or amorphous domains of D–A polymers determines the polarity switching of the Seebeck coefficient.

Efficient organic electronic devices are fabricated from both small molecules and disperse polymers, but materials with characteristics in between remain largely unexplored. Here, we present a gram-scale synthesis for a series of discrete n-type oligomers comprising alternating naphthalene diimide (NDI) and bithiophene (T2). Using C-H activation, discrete oligomers of type T2-(NDI-T2)n (n ≤ 7) and persistence lengths up to ∼10 nm are made. The absence of protection/deprotection reactions and the mechanistic nature of Pd-catalyzed C-H activation allow one to produce symmetrically terminated species almost exclusively, which is key to the fast preparation, high yields, and the general success of the reaction pathway. The reaction scope includes different thiophene-based monomers, end-capping to yield NDI-(T2-NDI)n (n ≤ 8), and branching at T2 units by nonselective C-H activation under certain conditions. We show how the optical, electronic, thermal, and structural properties depend on oligomer length along with a comparison to the disperse, polymeric analogue PNDIT2. From theory and experiments, we find that the molecular energy levels are not affected by chain length resulting from the strong donor-acceptor system. Absorption maxima saturate for n = 4 in vacuum and for n = 8 in solution. Linear oligomers T2-(NDI-T2)n are highly crystalline with large melting enthalpies up to 33 J/g; NDI-terminated oligomers show reduced crystallinity, stronger supercooling, and more phase transitions. Branched oligomers and those with bulky thiophene comonomers are amorphous. Large oligomers exhibit similar packing characteristics compared to PNDIT2, making these oligomers ideal models to study length-structure-function relationships at constant energy levels.