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N-doping plays an irreplaceable role in controlling the electron concentration of organic semiconductors thus to improve performance of organic semiconductor devices. However, compared with many mature p-doping methods, n-doping of organic semiconductor is still of challenges. In particular, dopant stability/processability, counterion-semiconductor immiscibility and doping induced microstructure non-uniformity have restricted the application of n-doping in high-performance devices. Here, we report a computer-assisted screening approach to rationally design of a triaminomethane-type dopant, which exhibit extremely high stability and strong hydride donating property due to its thermally activated doping mechanism. This triaminomethane derivative shows excellent counterion-semiconductor miscibility (counter cations stay with the polymer side chains), high doping efficiency and uniformity. By using triaminomethane, we realize a record n-type conductivity of up to 21 S cm −1 and power factors as high as 51 μW m −1  K −2 even in films with thicknesses over 10 μm, and we demonstrate the first reported all-polymer thermoelectric generator. Realizing efficient n-doping in organic thermoelectrics remains a challenge due to dopant-semiconductor immiscibility, poor dopant stability and low doping efficiency. Here, the authors use computer-assisted screening to develop n-dopants for thermoelectric polymers that show record power factors.

Over the past three decades, the mobility of organic field‐effect transistors (OFETs) has been improved from 10−5 up to over 10 cm2 V−1 s−1, which reaches or has already satisfied the requirements of demanding applications. However, pronounced nonideal behaviors in current–voltage characteristics are commonly observed, which indicates that the reported mobilities may not truly reflect the device properties. Herein, a comprehensive understanding of the origins of several observed nonidealities (downward, upward, double‐slope, superlinear, and humped transfer characteristics) is summarized, and how to extract comparatively reliable mobilities from nonideal behaviors in OFETs is discussed. Combining an overview of the ideal and state‐of‐the‐art OFETs, considerable possible approaches are also provided for future OFETs. Nonideal current–voltage characteristics make the mobility that truly reflects the device performance hard to be extracted. A fundamental understanding is necessary to overcome this issue. Herein, the observed nonideal behaviors of organic field‐effect transistors are summarized and analyzed, and solutions for future device engineering toward ideal organic field‐effect transistors are provided.

The field of organic electronics has profited from the discovery of new conjugated semiconducting polymers that have molecular backbones which exhibit resilience to conformational fluctuations, accompanied by charge carrier mobilities that routinely cross the 1 cm 2 /Vs benchmark. One such polymer is indacenodithiophene-co-benzothiadiazole. Previously understood to be lacking in microstructural order, we show here direct evidence of nanosized domains of high order in its thin films. We also demonstrate that its device-based high-performance electrical and thermoelectric properties are not intrinsic but undergo rapid stabilization following a burst of ambient air exposure. The polymer’s nanomechanical properties equilibrate on longer timescales owing to an orthogonal mechanism; the gradual sweating-out of residual low molecular weight solvent molecules from its surface. We snapshot the quasistatic temporal evolution of the electrical, thermoelectric and nanomechanical properties of this prototypical organic semiconductor and investigate the subtleties which play on competing timescales. Our study documents the untold and often overlooked story of a polymer device’s dynamic evolution toward stability. Organic polymer nanomechanics has been explored through precise nanometre-scale stiffness measurements in a high-mobility semiconducting polymer. Higher eigen-mode atomic force microscopy is used to measure nanomechnical variations in the film texture, as well as the nanoscale order in the material.

Thermoelectric materials, enabling direct waste-heat to electricity conversion, need to be highly electrically conducting while simultaneously thermally insulating. This is fundamentally challenging since electrical and thermal conduction usually change in tandem. In quasi-two-dimensional conjugated coordination polymer films we discover an advantageous thermoelectric transport regime, in which charge transport is defect-tolerant but heat propagation is defect-sensitive; it imparts the ideal mix of antithetical properties—temperature-activated, exceptionally low lattice thermal conductivities of 0.2 W m −1 K −1 below Kittel’s limit originating from small-amplitude, quasi-harmonic lattice dynamics with disorder-limited lifetimes and vibrational scattering length on the order of interatomic spacing, and high electrical conductivities up to 2000 S cm −1 with metallic temperature dependence, notably in poorly crystalline structures with paracrystallinity >10%. These materials offer attractive properties, such as ease of processing and defect tolerance, for applications, that require fast charge, but slow heat transport. Thermoelectric materials are required to be electrically conducting while thermally insulating, which can be challenging to achieve. Here, the authors report a thermoelectric transport regime with defect tolerant charge transport but defect intolerant heat propagation in two-dimensional coordination polymer films.

n‐Type organic electrochemical transistors (OECTs) and organic field‐effect transistors (OFETs) are less developed than their p‐type counterparts. Herein, polynaphthalenediimide (PNDI)‐based copolymers bearing novel fluorinated selenophene‐vinylene‐selenophene (FSVS) units as efficient materials for both n‐type OECTs and n‐type OFETs are reported. The PNDI polymers with oligo(ethylene glycol) (EG7) side chains P(NDIEG7‐FSVS), affords a high µC* of > 0.2 F cm−1 V−1 s−1, outperforming the benchmark n‐type Pg4NDI‐T2 and Pg4NDI‐gT2 by two orders of magnitude. The deep‐lying LUMO of −4.63 eV endows P(NDIEG7‐FSVS) with an ultra‐low threshold voltage of 0.16 V. Moreover, the conjugated polymer with octyldodecyl (OD) side chains P(NDIOD‐FSVS) exhibits a surprisingly low energetic disorder with an Urbach energy of 36 meV and an ultra‐low activation energy of 39 meV, resulting in high electron mobility of up to 0.32 cm2 V−1 s−1 in n‐type OFETs. These results demonstrate the great potential for simultaneously achieving a lower LUMO and a tighter intermolecular packing for the next‐generation efficient n‐type organic electronics. Novel PNDI‐based polymers bearing fluorinated selenophene‐vinylene‐selenophene (FSVS) are synthesized. The glycolated P(NDIEG7‐FSVS) with a deep‐lying LUMO of −4.63 eV gives an ultra‐low threshold voltage of 0.16 V, yielding a µC* > 0.2 F cm−1 V−1 s−1 in n‐type OECTs; the alkylated P(NDIOD‐FSVS), with a low Urbach energy of 36 meV and a low activation energy of 39 meV, exhibits electron mobility of > 0.3 cm2 V−1 s−1 in n‐type OFETs.

Thermoelectric (TE) technology attracts much attention due to the fact it can convert thermal energy into electricity and vice versa. Thin-film TE materials can be synthesized on different kinds of substrates, which offer the possibility of the control of microstructure and composition to higher TE power, as well as the development of novel TE devices meeting flexible and miniature requirements. In this work, we use magnetron sputtering to deposit N-type and P-type BiTe-based thin films on silicon, glass, and Kapton HN polyimide foil. Their morphology, microstructure, and phase constituents are studied by SEM/EDX, XRD, and TEM. The electrical conductivity, thermal conductivity, and Seebeck coefficient of the thin film are measured by a special in-plane advanced test system. The output of electrical power (open-circuit voltage and electric current) of the thin film is measured by an in-house apparatus at different temperature gradient. The impact of deposition parameters and the thickness, width, and length of the thin film on the power output are also investigated for optimizing the thin-film flexible TE device to harvest thermal energy.

Thermoelectric materials, enabling direct waste-heat to electricity conversion, need to be highly electrically conducting while simultaneously thermally insulating. This is fundamentally challenging since electrical and thermal conduction are usually coupled. Here, we discover that quasi-2D conjugated coordination polymer films exhibit this ideal mix of antithetical properties due to coexistence of defect-tolerant charge transport and defect-sensitive heat propagation. The former is highlighted by the highest conductivities > 2000 S cm-1 with metallic temperature dependence observed in disordered films with paracrystallinity > 10%, while the latter manifests in low, temperature-activated lattice thermal conductivities (< 0.38 W m-1 K-1) originating from small-amplitude, quasi-harmonic lattice dynamics with disorder-limited lifetimes and vibrational scattering length on the order of interatomic spacing. Based on temperature-dependent thermoelectric and magnetotransport experiments we identify a two-carrier (hole-electron), ambipolar metallic transport regime as the origin of relatively small Seebeck coefficients in these materials. Our findings identify conjugated coordination polymers as attractive materials for applications in thermoelectric energy harvesting, (bio)electronics and energy storage.