Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic‐scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer‐like atomic‐scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III‐V, or II‐VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
The development of layer-oriented two-dimensional conjugated metal–organic frameworks (2D c-MOFs) enables access to direct charge transport, dial-in lateral/vertical electronic devices, and the unveiling of transport mechanisms but remains a significant synthetic challenge. Here we report the novel synthesis of metal-phthalocyanine-based p-type semiconducting 2D c-MOF films (Cu2[PcM–O8], M = Cu or Fe) with an unprecedented edge-on layer orientation at the air/water interface. The edge-on structure formation is guided by the preorganization of metal-phthalocyanine ligands, whose basal plane is perpendicular to the water surface due to their π–π interaction and hydrophobicity. Benefiting from the unique layer orientation, we are able to investigate the lateral and vertical conductivities by DC methods and thus demonstrate an anisotropic charge transport in the resulting Cu2[PcCu–O8] film. The directional conductivity studies combined with theoretical calculation identify that the intrinsic conductivity is dominated by charge transfer along the interlayer pathway. Moreover, a macroscopic (cm2 size) Hall-effect measurement reveals a Hall mobility of ∼4.4 cm2 V–1 s–1 for the obtained Cu2[PcCu–O8] film. The orientation control in semiconducting 2D c-MOFs will enable the development of various optoelectronic applications and the exploration of unique transport properties.
All‐inorganic halide perovskite materials have recently emerged as outstanding materials for optoelectronic applications. However, although critical for developing novel technologies, the influence of charge traps on charge transport in all‐inorganic systems still remains elusive. Here, the charge transport properties in cesium lead bromide, nanowire films are probed using a field‐effect transistor geometry. Field‐effect mobilities of μFET = 4 × 10−3 cm−2 V−1 s−1 and photoresponsivities in the range of R = 25 A W−1 are demonstrated. Furthermore, charge transport both with and without illumination is investigated down to cryogenic temperatures. Without illumination, deep traps dominate transport and the mobility freezes out at low temperatures. Despite the presence of deep traps, when illuminating the sample, the field‐effect mobility increases by several orders of magnitude and even phonon‐limited transport characteristics are visible. This can be seen as an extension to the notion of “defect tolerance” of perovskite materials that has solely been associated with shallow traps. These findings provide further insight in understanding charge transport in perovskite materials and underlines that managing deep traps can open up a route to optimizing optoelectronic devices such as solar cells or phototransistors operable also at low light intensities.
Intrinsic charge transport in molecularly thin organic semiconducting crystals is critically sensitive to the quality of the interfaces required to perform the electrical measurements. Most prominent are the dielectric–semiconductor and semiconductor–metal interface. While impacts from the latter on charge transport can be extracted by four‐terminal measurements, the impact of the dielectric interface can only be minimized, typically by utilizing inert dielectrics. Here, it is shown that charge transport in organic field‐effect transistors based on the n‐type small molecule N, N′‐di((S)‐1‐methylpentyl)‐1,7(6)‐dicyano‐perylene‐3,4:9,10‐bis(dicarboximide) (PDI1MPCN2) can be improved up to one order of magnitude by using hexagonal boron nitride (h‐BN) as dielectric, compared to a standard SiO2 substrate. Using temperature‐dependent electrical measurements, the charge‐transport properties of devices are systematically analyzed, and high four‐terminal mobilities of up to 5.0 cm2 V−1 s−1 are obtained. The high mobility likely stems from decreased charge‐carrier trapping at the semiconductor‐dielectric interface due to the smooth surface of the inert h‐BN. Nevertheless, the temperature dependencies of the mobility, threshold voltage, and interface‐state trap density suggest that charge‐carrier trapping at the dielectric‐semiconductor interface still exists. By comparing the data to transport studies performed on thin air‐gapped organic films, it is concluded that an interfacial layer (likely water or solvent residues) between h‐BN and the monolayer PDI1MPCN2 causes charge trapping.
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