The charge transport properties of conjugated polymers are commonly limited by the energetic disorder. Recently, several amorphous conjugated polymers with planar backbone conformations and low energetic disorder have been investigated for applications in field-effect transistors and thermoelectrics. However, there is a lack of strategy to finely tune the interchain π-π contacts of these polymers that severely restricts the energetic disorder of interchain charge transport. Here, we demonstrate that it is feasible to achieve excellent conductivity and thermoelectric performance in polymers based on thiophene-fused benzodifurandione oligo( p -phenylenevinylene) through reducing the crystallization rate of side chains and, in this way, carefully controlling the degree of interchain π-π contacts. N-type (p-type) conductivities of more than 100 S cm ⁻¹ (400 S cm ⁻¹ ) and power factors of more than 200 μW m ⁻¹ K ⁻² (100 μW m ⁻¹ K ⁻² ) were achieved within a single polymer doped by different dopants. It further demonstrated the state-of-the-art power output of the first flexible single-polymer thermoelectric generator.

Colloidal quantum dots (QDs) have illuminated computer monitors and television screens due to their fascinating color-tunable properties depending on the size. Here, the electroluminescence (EL) wavelength of perovskite LEDs was tuned via the atomic layer number (ALN) of nanoplates (NPs) instead of the “size” in conventional QDs. We demonstrated efficient LEDs with controllably tailored emission from n = 3, 4, 5, and ≥7 ALN perovskite NPs with specific and discrete major peaks at 607, 638, 669, and 728 nanometers. These LEDs demonstrated peak external quantum efficiency (EQE) of 26.8% and high wavelength reproducibility with less than 1 to 2 nm difference between batches. High color stability without observable EL spectral change and operating stability with the best T ₅₀ of 267 minutes at 1.0 milliampere per square centimeter was also achieved. This work demonstrates a concept of tailoring specific ALN emission with fixed wavelengths, shedding light on efficient, emission-discrete, and color-stable LEDs for next-generation display.

2D conjugated coordination polymers (cCPs) based on square‐planar transition metal‐complexes (such as MO₄, M(NH)₄, and MS₄, M = metal) are an emerging class of (semi)conducting materials that are of great interest for applications in supercapacitors, catalysis, and thermoelectrics. Finding synthetic approaches to high‐performance nickel‐nitrogen (Ni‐N) based cCP films is a long‐standing challenge. Here, a general, dynamically controlled on‐surface synthesis that produces highly conductive Ni‐N‐based cCP films is developed and the thermoelectric properties as a function of the molecular structure and their dependence on interactions with ambient atmosphere are studied. Among the four studied cCPs with different ligand sizes hexaminobenzene‐ and hexaaminotriphenylene‐based films exhibit record electrical conductivity (100–200 S cm^–1) in this Ni‐N based cCP family, which is one order of magnitude higher than previous reports, and the highest thermoelectric power factors up to 10 µW m^–1 K^–2 among reported 2D cCPs. The transport physics of these films is studied and it is shown that depending on the host‐guest interaction with oxygen/water the majority carrier type and the value of the Seebeck coefficient can be largely regulated. The high conductivity is likely reflecting good interconnectivity between (small) ordered domains and grain boundaries supporting disordered metallic transport.

The migration of ionic defects and electrochemical reactions with metal electrodes remains one of the most important research challenges for organometal halide perovskite optoelectronic devices. There is still a lack of understanding of how the formation of mobile ionic defects impact charge carrier transport and operational device stability, particularly in perovskite field‐effect transistors (FETs), which tend to exhibit anomalous device characteristics. Here, the evolution of the n‐type FET characteristics of one of the most widely studied materials, Cs_0.05FA_0.17MA_0.78PbI_3, is investigated during repeated measurement cycles as a function of different metal source–drain contacts and precursor stoichiometry. The channel current increases for high work function metals and decreases for low work function metals when multiple cycles of transfer characteristics are measured. The cycling behavior is also sensitive to the precursor stoichiometry. These metal/stoichiometry‐dependent device non‐idealities are correlated with the quenching of photoluminescence near the positively biased electrode. Based on elemental analysis using electron microscopy the observations can be understood by an n‐type doping effect of metallic ions that are created by an electrochemical interaction at the metal–semiconductor interface and migrate into the channel. The findings improve the understanding of ion migration, contact reactions, and the origin of non‐idealities in lead triiodide perovskite FETs.

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 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.