CZTSSe thin films were deposited by selenization of single step electrodeposited CZTS thin films. The properties of CZTSSe thin films were significantly improved by optimizing Se vaporization ...temperature.
•CZTS precursor thin films are prepared by single step electrodeposition method.•The properties of CZTSSe thin films depend on Se vaporization temperature.•The compact CZTSSe thin films can be used as absorber in thin film solar cells.
Cu2ZnSn(SxSe1−x)4 (CZTSSe) thin films are prepared by selenizing a single-step electrodeposited Cu–Zn–Sn–S precursor. The effect of the selenium (Se) vaporization temperature on the properties of CZTSSe thin films is systematically investigated. The position of the (112) peak is systematically shifted to lower 2θ values when the Se vaporization temperature increases. The Raman spectra of CZTSSe films show bimodal behavior. The microstructure and film thickness significantly improve with increasing Se vaporization temperature. The increased Se incorporation in CZTSSe films with the increase of the Se vaporization temperature is demonstrated using a compositional analysis. The band gap energy of CZTSSe thin films is tuned in the range of 1.40–1.08eV by varying the Se vaporization temperature.
•Failure of GeSn nanowire growth was found when Sn and SnO2 thin films were used.•Sparse catalyst and inhibition of catalyst wetting are two key factors to ensure the growth of GeSn nanowires.•Ge ...nanocrystals with good quality were grown from ITO thin films when there is no interfacial SiOx layer.•Controlling of the morphology of GeSn nanowires is realized by changing the annealing environments.
The formation of Sn catalyst nanoparticles (NPs) for the growth of GeSn nanowires (NWs) requires the identification of suitable Sn-containing precursors. In this work, various Sn-containing precursors such as Sn, SnO2 and indium tin oxide (ITO) thin films as well as SnO2 nanoparticles have been investigated. Sn and SnO2 thin films did not produce NWs. This reveals that the catalyst density, as well as their wetting on the amorphous layer, play vital roles on the growth of GeSn NWs. Conversely, Ge nanocrystals (NCs) were successfully grown from ITO thin films deposited on c-Si substrates. A good crystallinity was obtained when there is no interfacial SiOx layer on the crystalline Si substrate. Finally, using SnO2 NPs allowed us to grow GeSn NWs. Their morphology is strongly impacted by the annealing environment: hydrogen atmosphere with different pressures or hydrogen plasma, the later providing the best results. The nanostructure and composition of GeSn NWs were investigated in detail. These results could pave the way to grow in-plane Ge nanostructures within several types of Sn-containing materials.
In perovskite solar cells, the interfaces between the perovskite and charge-transporting layers contain high concentrations of defects (about 100 times that within the perovskite layer), ...specifically, deep-level defects, which substantially reduce the power conversion efficiency ofthe devices1-3. Recent efforts to reduce these interfacial defects have focused mainly on surface passivation4-6. However, passivating the perovskite surface that interfaces with the electron-transporting layer is difficult, because the surface-treatment agents on the electron-transporting layer may dissolve while coating the perovskite thin film. Alternatively, interfacial defects may not be a concern if a coherent interface could be formed between the electron-transporting and perovskite layers. Here we report the formation of an interlayer between a SnO2 electron-transporting layer and a halide perovskite light-absorbing layer, achieved by coupling Cl-bonded SnO2 with a Cl-containing perovskite precursor. This interlayer has atomically coherent features, which enhance charge extraction and transport from the perovskite layer, and fewer interfacial defects. The existence of such a coherent interlayer allowed us to fabricate perovskite solar cells with a power conversion efficiency of 25.8 per cent (certified 25.5 per cent)under standard illumination. Furthermore, unencapsulated devices maintained about 90 per cent oftheir initial efficiency even after continuous light exposure for 500 hours. Our findings provide guidelines for designing defect-minimizing interfaces between metal halide perovskites and electron-transporting layers.
Since the report of the first diketopyrrolopyrrole (DPP)‐based polymer semiconductor, such polymers have received considerable attention as a promising candidate for high‐performance polymer ...semiconductors in organic thin‐film transistors (OTFTs). This Progress Report summarizes the advances in the molecular design of high‐mobility DPP‐based polymers reported in the last few years, especially focusing on the molecular design of these polymers in respect of tuning the backbone and side chains, and discussing the influences of structural modification of the backbone and side chains on the properties and device performance of corresponding DPP‐based polymers. This provides insights for the development of new and high‐mobility polymer semiconductors.
The advances in molecular design of high‐mobility DPP‐based polymers reported in the past few years are summarized, focusing on the strategy for synthesis of these polymers with respect to tuning the backbone and side chains. The relationships between the chemical structure, molecular packing, transistor characteristics, for example, are discussed.
All‐solid‐state (ASS) lithium metal batteries (LMBs) are considered the most promising next‐generation batteries due to their superior safety and high projected energy density. To access the ...practically desired high energy density of ASS LMBs, an ultrathin solid‐state electrolyte (SSE) film with fast ion‐transport capability presents as an irreplaceable component to reduce the proportion of inactive materials in ASS batteries. In this contribution, an ultrathin (60 µm), flexible, and free‐standing argyrodite (Li6PS5Cl) SSE film is designed through a self‐limited strategy. A chemically compatible cellulose membrane is employed as the self‐limiting skeleton that not only defined the thinness of the sulfide SSE film but also strengthened its mechanical properties. The ionic conductivity of the SSE film reaches up to 6.3 × 10−3 S cm−1 at room temperature, enabling rapid lithium‐ion transportation. The self‐limited SSE thin films are evaluated in various ASS LMBs with different types of cathode (sulfur and lithium titanate) and anode materials (lithium and lithium‐indium alloy) at both mold‐cell and pouch‐cell levels, demonstrating a stable performance and high‐rate capability. This study provides a general strategy for the rational design of an SSE thin film towards high‐energy‐density ASS batteries.
An ultrathin, flexible, and free‐standing argyrodite solid‐state electrolyte film is designed through a self‐limited strategy. The ionic conductivity of the SSE film reaches up to 6.3 × 10−3 S cm−1 at room temperature, enabling rapid lithium‐ion transportation in all‐solid‐state batteries.
van der Waals heterostructures constitute a new class of artificial materials formed by stacking atomically thin planar crystals. We demonstrated band structure engineering in a van der Waals ...heterostructure composed of a monolayer graphene flake coupled to a rotationally aligned hexagonal boron nitride substrate. The spatially varying interlayer atomic registry results in both a local breaking of the carbon sublattice symmetry and a long-range moiré superlattice potential in the graphene. In our samples, this interplay between short-and long-wavelength effects resulted in a band structure described by isolated superlattice minibands and an unexpectedly large band gap at charge neutrality. This picture is confirmed by our observation of fractional quantum Hall states at ±5/3 filling and features associated with the Hofstadter butterfly at ultrahigh magnetic fields.
Improving transistors with nanomaterials
High-performance silicon transistors and thin-film transistors used in display technologies are fundamentally limited to miniaturization. Incorporating ...nanomaterials—such as carbon nanotubes, graphene, and related two-dimensional materials like molybdenum disulfide—into these devices as gate materials may circumvent some of these limitations. Franklin reviews the opportunities and challenges for incorporating nanomaterials into transistors to improve performance. Because high-performance transistors are distinct from thin-film transistors, incorporating them into flexible or transparent platforms raises new challenges.
Science
, this issue
10.1126/science.aab2750
For more than 50 years, silicon transistors have been continuously shrunk to meet the projections of Moore’s law but are now reaching fundamental limits on speed and power use. With these limits at hand, nanomaterials offer great promise for improving transistor performance and adding new applications through the coming decades. With different transistors needed in everything from high-performance servers to thin-film display backplanes, it is important to understand the targeted application needs when considering new material options. Here the distinction between high-performance and thin-film transistors is reviewed, along with the benefits and challenges to using nanomaterials in such transistors. In particular, progress on carbon nanotubes, as well as graphene and related materials (including transition metal dichalcogenides and X-enes), outlines the advances and further research needed to enable their use in transistors for high-performance computing, thin films, or completely new technologies such as flexible and transparent devices.
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