Copper Sulfide (CuxS) Nanowire‐in‐Carbon Composites Formed from Direct Sulfurization of the Metal‐Organic Framework HKUST‐1 and Their Use as Li‐Ion Battery Cathodes

Li‐ion batteries containing cost‐effective, environmentally benign cathode materials with high specific capacities are in critical demand to deliver the energy density requirements of electric vehicles and next‐generation electronic devices. Here, the phase‐controlled synthesis of copper sulfide (Cu_xS) composites by the temperature‐controlled sulfurization of a prototypal Cu metal‐organic framework (MOF), HKUST‐1 is reported. The tunable formation of different Cu_xS phases within a carbon network represents a simple method for the production of effective composite cathode materials for Li‐ion batteries. A direct link between the sulfurization temperature of the MOF and the resultant Cu_xS phase formed with more Cu‐rich phases favored at higher temperatures is further shown. The Cu_xS/C samples are characterized through X‐ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy, and energy dispersive X‐ray spectroscopy (EDX) in addition to testing as Li‐ion cathodes. It is shown that the performance is dependent on both the Cu_xS phase and the crystal morphology with the Cu_1.8S/C‐500 material as a nanowire composite exhibiting the best performance, showing a specific capacity of 220 mAh g^?1 after 200 charge/discharge cycles.     

In Situ Formation of Copper‐Based Hosts Embedded within 3D N‐Doped Hierarchically Porous Carbon Networks for Ultralong Cycle Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg^?1 and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co‐doped hierarchically porous graphitic carbon network developed through a freeze‐drying method (denoted as 3D Cu@NC‐F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li–S batteries. The porous carbon network consisting of 2D cross‐linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N‐doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC‐F network, the in situ grown copper sulfide (Cu_xS) embedded within Cu_xS@NC/S‐F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the Cu_xS@NC/S‐F composites' electrode exhibits an initial capacity of 1432 mAh g^?1 and maintains 1169 mAh g^?1 after 120 cycles, with a coulombic efficiency of nearly 100%.     

Size‐Controlled Synthesis of Cu2‐xE (E = S,Se) Nanocrystals with Strong Tunable Near‐Infrared Localized Surface Plasmon Resonance and High Conductivity in Thin Films

A facile method for preparing highly self‐doped Cu_2‐xE (E = S, Se) nanocrystals (NCs) with controlled size in the range of 2.8–13.5 nm and 7.2–16.5 nm, for Cu_2‐xS and Cu_2‐xSe, respectively, is demonstrated. Strong near‐infrared localized surface plasmon resonance absorption is observed in the NCs, indicating that the as‐prepared particles are heavily p‐doped. The NIR plasmonic absorption is tuned by varying the amount of oleic acid used in synthesis. This effect is attributed to a reduction in the number of free carriers through surface interaction of the deprotonated carboxyl functional group of oleic acid with the NCs. This approach provides a new pathway to control both the size and the cationic deficiency of Cu_2‐xSe and Cu_2‐xS NCs. The high electrical conductivity exhibited by these NPs in metal‐semiconductor‐metal thin film devices shows promise for applications in printable field‐effect transistors and microelectronic devices.     

Dynamic radiative properties of the Cu(In,Ga)Se2 layer during the co‐evaporation process

A study of the wavelength‐integrated emissivity has been performed on the optical stack Cu_xSe/Cu(In,Ga)Se₂/Mo. The wavelength interval used in the study was 2–20 µm, which covers 95% of the radiated heat from a black body heated to 500°C. Substrate temperatures around 500°C are commonly used in production of Cu(In,Ga)Se₂ thin films for solar cells. The integrated emissivity was obtained from directional reflectivity measurements of experimental samples with different thicknesses of the Cu_xSe layers. It was subsequently compared to the emissivity from numerical simulations based on newly obtained values of the refractive index values for Cu(In,Ga)Se₂ and Cu_xSe at these wavelengths. Good agreement was found between the measured and simulated values. At a Cu(In,Ga)Se₂ thickness of 1.8 µm and a Mo thickness of 400 nm, a maximum in the integrated emissivity was found for a Cu_xSe thickness of 30 nm. The results are valuable input into understanding the dynamics of the change in emissivity between Cu‐rich Cu(In,Ga)Se₂ with segregated Cu_xSe and Cu‐poor single phase Cu(In,Ga)Se₂ at temperatures around 500°C. In co‐evaporation of Cu(In,Ga)Se₂, this emissivity change is often monitored and used as a process control (end‐point detection). Copyright © 2010 John Wiley & Sons, Ltd.     

Precise Tuning of (YBa2Cu3O7‐δ)1‐x:(BaZrO3)x Thin Film Nanocomposite Structures

Self‐assembled nanocomposite films and coatings have huge potential for many functional and structural applications. However, control and manipulation of the nanostructures is still at very early stage. Here, guidelines are established for manipulating the types of composite structures that can be achieved. In order to do this, a well studied (YBa₂Cu₃O_7‐δ)_1‐x:(BaZrO₃)_x ‘model’ system is used. A switch from BaZrO₃ nanorods in YBa₂Cu₃O_7‐δ matrix to planar, horizontal layered plates is found with increasing x, with a transitional cross‐ply structure forming between these states at x = 0.4. The switch is related to a release in strain energy which builds up in the YBa₂Cu₃O_7‐δ with increasing x. At x = 0.5, an unusually low strain state is observed in the planar composite structure, which is postulated to arise from a pseudo‐spinodal mechanism.     

Mg3+δSbxBi2−x Family: A Promising Substitute for the State‐of‐the‐Art n‐Type Thermoelectric Materials near Room Temperature

The Bi₂Te_3?xSe_x family has constituted n‐type state‐of‐the‐art thermoelectric materials near room temperature (RT) for more than half a century, which dominates the active cooling and novel heat harvesting application near RT. However, the drawbacks of a brittle nature and Te‐content restricts the possibility for exploring potential applications. Here, it is shown that the Mg_3+δSb_xBi_2?x family ((ZT)_avg = 1.05) could be a promising substitute for the Bi₂Te_3?xSe_x family ((ZT)_avg = 0.9–1.0) in the temperature range of 50–250 °C based on the comparable thermoelectric performance through a synergistic effect from the tunable bandgap using the alloy effect and the suppressible Mg‐vacancy formation using an interstitial Mn dopant. The former is to shift the optimal thermoelectric performance to near RT, and the latter is helpful to partially decouple the electrical transport and thermal transport in order to get an optimal RT power factor. The positive temperature dependence of the bandgap suggests this family is also a superior medium‐temperature thermoelectric material for the significantly suppressed bipolar effect. Furthermore, a two times higher mechanical toughness, compared with the Bi₂Te_3?xSe_x family, allows for a promising substitute for state‐of‐the‐art n‐type thermoelectric materials near RT.     

Enhanced Thermoelectric Performance and Service Stability of Cu2Se Via Tailoring Chemical Compositions at Multiple Atomic Positions

Liquid‐like thermoelectric (TE) materials have the advantages of ultrahigh performance, low cost, and environment friendly, but their stability is greatly limited by the possible Cu/Ag deposition under a large current and/or temperature gradient. The pratical application based on liquid‐like TE materials requires both a high TE figure of merit (zT) for high energy conversion efficiency and large critical voltage for good stability, but they are very difficult to be simultaneously achieved in one material. In this work, both the zT and critical voltage are simultaneously optimized in Cu₂Se via tailoring chemical compositions at multiple atomic positions, i.e., introducing Cu deficiency at the Cu‐sites to lower Cu ion chemical potential and alloying sulfur at the Se‐sites to reduce carrier concentrations. A maximum zT of 2.0 at 1000 K has been successfully achieved for Cu_1.96Se_0.8S_0.2, about a 30% improvement over that for Cu₂Se. More importantly, Cu_1.96Se_0.8S_0.2 demonstrates a much higher critical voltage than Cu₂Se, yielding a greatly enhanced service stability under the conditions with/without a temperature gradient. An Ni/Mo/Cu_1.96Se_0.8S_0.2 TE unileg is successfully fabricated with a stable power output even after 400 thermal cycles between 473 and 873 K. This study greatly accelerates the real application of Cu₂Se‐based liquid‐like materials.     

Applications of Tin Sulfide‐Based Materials in Lithium‐Ion Batteries and Sodium‐Ion Batteries

SnS_x (x = 1, 2) compounds are composed of earth‐abundant elements and are nontoxic and low‐cost materials that have received increasing attention as energy materials over the past decades, owing to their huge potential in batteries. Generally, SnS_x materials have excellent chemical stability and high theoretical capacity and reversibility due to their unique 2D‐layered structure and semiconductor properties. As a promising matrix material for storing different alkali metal ions through alloying/dealloying reactions, SnS_x compounds have broad electrochemical prospects in batteries. Herein, the structural properties of SnS_x materials and their advantages as electrode materials are discussed. Furthermore, detailed accounts of various synthesis methods and applications of SnS_x materials in lithium‐ion batteries, sodium‐ion batteries, and other new rechargeable batteries are emphasized. Ultimately, the challenges and opportunities for future research on SnS_x compounds are discussed based on the available academic knowledge, including recent scientific advances.     

Self‐Established Rapid Magnesiation/De‐Magnesiation Pathways in Binary Selenium–Copper Mixtures with Significantly Enhanced Mg‐Ion Storage Reversibility

Rechargeable magnesium/sulfur (Mg/S) and magnesium/selenium (Mg/Se) batteries are characterized by high energy density, inherent safety, and economical effectiveness, and therefore, are of great scientific and technological interest. However, elusive challenges, including the limited charge storage capacity, low Coulombic efficiency, and short cycle life, have been encountered due to the sluggish electrochemical kinetics and severe shuttles of ploysulfides (polyselenide). Taking selenium as model paradigm, a new and reliable Mg‐Se chemistry is proposed through designing binary selenium‐copper (Se‐Cu) cathodes. An intriguing effect of Cu powders on the electrochemical reaction pathways of the active Se microparticles is revealed in a way of forming Cu₃Se₂ intermediates, which induces an unconventional yet reversible two‐stage magnesiation mechanism: Mg‐ions first insert into Cu₃Se₂ phases; in a second step Cu‐ions in the Mg_2xCu₃Se₂ lattice exchange with Mg‐ions. As expected, binary Se‐Cu electrodes show significantly improved reversibility and elongated cycle life. More bracingly, Se/C nanostructures fabricated by facile blade coating Se nanorodes onto copper foils exhibit high output power and capacity (696.0 mAh g^?1 at 67.9 mA g^?1), which outperforms all previously reported Mg/Se batteries. This work envisions a facile and reliable strategy to achieve better reversibility and long‐term durability of selenium (sulfur) electrodes.     

The Formation of Performance Enhancing Pseudo‐Composites in the Highly Active La1–xCaxFe0.8Ni0.2O3 System for IT‐SOFC Application

The La_1–xCa_xFe_0.8Ni_0.2O_3–δ (0 ≤ x ≤ 0.9) system is investigated for potential application as a cathode material for intermediate temperature solid oxide fuel cells (IT‐SOFCs). A broad range of experimental techniques have been utilized in order to elucidate the characteristics of the entire compositional range. Low A‐site Ca content compositions (x ≤ 0.4) feature a single perovskite solid solution. Compositions with 40% Ca content (x = 0.4) exhibit the highest electrical and ionic conductivities of these single phase materials (250 and 1.9 × 10^?3 S cm^?1 at 800 °C, respectively), a level competitive with state‐of‐the‐art (La,Sr)(Fe,Co)O₃. Between 40 and 50% Ca content (0.4 > x > 0.5) a solubility limit is reached and a secondary, brownmillerite‐type phase appears for all higher Ca content compositions (0.5 ≤ x ≤ 0.9). While typically seen as detrimental to electrochemical performance in cathode materials, this phase brings with it ionic conductivity at operational temperatures. This gives rise to the effective formation of pseudo‐composite materials which feature significantly enhanced performance characteristics, while also providing the closest match in thermal expansion behavior to typical electrolyte materials. This all comes with the advantage of being produced through a simple, single‐step, low‐cost production route without the issues associated with typical composite materials. The highest performing pseudo‐composite material (x = 0.5) exhibits electronic conductivity of 300–350 S cm^?1 in the 600–800 °C temperature range while the best polarisation resistance (R_p) values of approximately 0.2 Ω cm² are found in the 0.5 ≤ x ≤ 0.7 range.     

Engineering Solar Cell Absorbers by Exploring the Band Alignment and Defect Disparity: The Case of Cu‐ and Ag‐Based Kesterite Compounds

The development of kesterite Cu₂ZnSn(S,Se)₄ thin‐film solar cells is currently hindered by the large deficit of open‐circuit voltage (V_oc), which results from the easy formation of Cu_Zn antisite acceptor defects. Suppressing the formation of Cu_Zn defects, especially near the absorber/buffer interface, is thus critical for the further improvement of kesterite solar cells. In this paper, it is shown that there is a large disparity between the defects in Cu‐ and Ag‐based kesterite semiconductors, i.e., the Cu_Zn or Cu_Cd acceptor defects have high concentration and are the dominant defects in Cu₂ZnSn(S,Se)₄ or Cu₂CdSnS₄, but the Ag_Zn acceptor has only a low concentration and the dominant defects are donors in Ag₂ZnSnS₄. Therefore, the Cu‐based kesterites always show p‐type conductivity, while the Ag‐based kesterites show either intrinsic or weak n‐type conductivity. Based on this defect disparity and calculated band alignment, it is proposed that the V_oc limit of the kesterite solar cells can be overcome by alloying Cu₂ZnSn(S,Se)₄ with Ag₂ZnSn(S,Se)₄, and the composition‐graded (Cu,Ag)₂ZnSn(S,Se)₄ alloys should be ideal light‐absorber materials for achieving higher efficiency kesterite solar cells.     

A Three Component Self‐Assembled Epitaxial Nanocomposite Thin Film

A self‐assembled three phase epitaxial nanocomposite film is grown consisting of ≈3 nm diameter fcc metallic Cu nanorods within square prismatic SrO rocksalt nanopillars in a Sr(Ti,Cu)O_3‐δ perovskite matrix. Each phase has an epitaxial relation to the others. The core–shell‐matrix structures are grown on SrTiO₃ substrates and can also be integrated onto Si using a thin SrTiO₃ buffer. The structure is made by pulsed laser deposition in vacuum from a SrTi_0.75Cu_0.25O₃ target, and formed as a result of the limited solubility of Cu in the perovskite matrix. Wet etching removes the 3 nm diameter Cu nanowires leaving porous SrO pillars. The three‐phase nanocomposite film is used as a substrate for growing a second epitaxial nanocomposite consisting of CoFe₂O₄ spinel pillars in a BiFeO₃ perovskite matrix, producing dramatic effects on the structure and magnetic properties of the CoFe₂O₄. This three‐phase vertical nanocomposite provides a complement to the well‐known two‐phase nanocomposites, and may offer a combination of properties of three different materials as well as additional avenues for strain‐mediated coupling within a single film.     

Wide‐Range‐Tunable p‐Type Conductivity of Transparent CuI1−xBrx Alloy

Transparent p‐type semiconductors with wide‐range tunability of the hole density are rare. Developing such materials is a challenge in the field of transparent electronics that utilize invisible electric circuits. In this paper, a CuI–CuBr alloy (CuI_1?xBr_x) is proposed as a hole‐density‐tunable p‐type transparent semiconductor that can be fabricated at room temperature. First‐principles calculations predict that the acceptor state originating from copper vacancies in CuBr is deeper than that in CuI, leading to the hypothesis that the hole density in CuI_1?xBr_x can be tuned over a wide range by varying x between 0 and 1. The experimental results support this hypothesis. The hole density in CuI_1?xBr_x polycrystalline alloy layers can be tuned by over three orders of magnitude (10¹⁷–10²⁰ cm^?3) by varying x. In other words, the p‐type conductivity of the CuI_1?xBr_x alloy shows metallic and semiconducting properties. Such alloy layers can be prepared at room temperature without sacrificing transparency. Furthermore, CuI_1?xBr_x forms transparent p–n diodes with n‐type amorphous In–Ga–Zn–O layers, and these diodes have satisfactory rectification performance. Therefore, CuI_1?xBr_x alloy is an excellent p‐type transparent semiconductor for which the p‐type conductivity can be tailored in a wide range.     

Cu2O Nanocrystal‐Templated Growth of Cu2S Nanocages with Encapsulated Au Nanoparticles and In‐Situ Transmission X‐ray Microscopy Study

Cubic and octahedral Cu₂O nanocrystals and Au–Cu₂O core–shell heterostructures are used as sacrificial templates for the growth of Cu₂S nanocages and Au–Cu₂S core–cage structures. A rapid sulfidation process involving a surface reaction of Cu₂O nanocrystals with Na₂S, followed by etching of the Cu₂O cores with HCl solution for ≈5 sec, results in the fabrication of Cu₂S cages with a wall thickness of 10–20 nm. Transmission electron microscopy characterization reveals the formation of crystalline walls and the presence of ultrasmall pores with sizes of 1 nm or less. Formation of Cu₂O–Cu₂S core–shell structures and their conversion into Cu₂S cages is verified by UV–vis absorption spectroscopy. X‐ray photoelectron spectra further confirm the composition of the cages as Cu₂S. The entire hollowing process via the Kirkendall effect is recorded using in‐situ transmission X‐ray microscopy. After shell formation, continuous ionic diffusion removes the interior Cu₂O. Intermediate structures with remaining central Cu₂O portions and bridging arms to the surrounding cages are observed. The nanocages are also shown to allow molecular transport: anthracene and pyrene penetration into the cages leads to enhanced fluorescence quenching immediately upon adsorption onto the surfaces of the encapsulated gold nanocrystals.     

Large‐Scale Synthesis of Long Crystalline Cu2‐xSe Nanowire Bundles by Water‐Evaporation‐Induced Self‐Assembly and Their Application in Gas Sensing

By a facile water evaporation process without adding any directing agent, Cu_2‐xSe nanowire bundles with diameters of 100–300 nm and lengths up to hundreds of micrometers, which comprise crystalline nanowires with diameters of 5–8 nm, are obtained. Experiments reveal the initial formation/stacking of CuSe nanoplates and the subsequent transformation to the Cu_2‐xSe nanowire bundles. A water‐evaporation‐induced self‐assembly (WEISA) mechanism is proposed, which highlights the driving force of evaporation in promoting the nanoplate stacking, CuSe‐to‐Cu_2‐xSe transformation and the growth/bundling of the Cu_2‐xSe nanowires. The simplicity, benignancy, scalability, and high‐yield of the synthesis of this important nanowire material herald its numerous applications. As one example, the use of the Cu_2‐xSe nanowire bundles as a photoluminescence‐type sensor of humidity is demonstrated, which shows good sensitivity, ideal linearity, quick response/recovery and long lifetime in a very wide humidity range at room temperature.     

One‐Step Preparation of Coaxial CdS–ZnS and Cd1–xZnxS–ZnS Nanowires

Preparation of coaxial (core–shell) CdS–ZnS and Cd_1–xZn_xS–ZnS nanowires has been achieved via a one‐step metal–organic chemical vapor deposition (MOCVD) process with co‐fed single‐source precursors of CdS and ZnS. Single‐source precursors of CdS and ZnS of sufficient reactivity difference were prepared and paired up to form coaxial nanostructures in a one‐step process. The sequential growth of ZnS on CdS nanowires was also conducted to demonstrate the necessity and advantages of the precursor co‐feeding practice for the formation of well‐defined coaxial nanostructures. The coaxial nanostructure was characterized and confirmed by high‐resolution transmission electron microscopy and corresponding energy dispersive X‐ray spectrometry analyses. The photoluminescence efficiencies of the resulting coaxial CdS–ZnS and Cd_1–xZn_xS–ZnS nanowires were significantly enhanced compared to those of the plain CdS and plain Cd_1–xZn_xS nanowires, respectively, owing to the effective passivation of the surface electronic states of the core materials by the ZnS shell.     

Strong Band Bowing Effects and Distinctive Optoelectronic Properties of 2H and 1T′ Phase‐Tunable MoxRe1–xS2 Alloys

Structure and energy band engineering of 2D materials via selective doping or phase modulation provide a significant opportunity to design them for optoelectronic devices. Here, the synthesis of high‐quality Mo_xRe_1–xS₂ alloys with tunable composition and phase structure via chemical vapor deposition growth is reported, and their novel energy band structures and optoelectronic properties are explored. The phase separation and structure reconstruction, which are found to be two serious problems in the synthesis of these alloys, are successfully suppressed through tuning their growth thermodynamics. As a result, the obtained Mo_xRe_1–xS₂ alloys have uniform composition, phase structure, and crystal orientation. Together with X‐ray photoelectron spectroscopy analysis and first‐principle calculation, the Re/Mo doping‐induced Fermi level up‐shift/down‐shift, new electronic states, and “sub‐gap” formation in Mo_xRe_1–xS₂ alloys are revealed. Especially, a strong band bowing effect is discovered in the Mo_xRe_1–xS₂ alloys with structure transition between 1T′ and 2H phases. Furthermore, these alloys reveal tunable conduction behavior from n‐type to bipolar and p‐type in 1T′ phase, as well as novel “bipolar‐like” electron conduction behavior in 2H alloys. The results highlight the unique alloying effects, which do not exist in the single‐phase 2D alloys, and provide the feasibility for potential applications in building novel electronic and optoelectronic devices.     

Alloy Engineering in Few‐Layer Manganese Phosphorus Trichalcogenides for Surface‐Enhanced Raman Scattering

Manganese phosphorus trichalcogenides are widely used in the field of photocatalysis and magnetic studies due to their broadband gaps. Herein, an alloy engineering method for the few‐layer manganese phosphorus trichalcogenides (MnPS_3–xSe_x, 0 ≤ x ≤ 3) in surface‐enhanced Raman scattering (SERS) is reported. A new strategy, with the coupling of exciton resonance (µ_ex) and photoinduced charge transfer (PICT), is applied to screen out materials for SERS enhancement. According to the calculation of density functional theory, the bandgap of manganese phosphorus trichalcogenides (MnPS₃) can be adjusted to match the band energy of Rhodamine 6G molecules by alloy engineering. Furthermore, a series of few‐layer MnPS_3–xSe_x (0 ≤ x ≤ 3) are fabricated to study the PICT‐induced SERS behavior under resonance excitation. The good performance with a detection limit down to 10^?9 m indicates that the synergistic resonances between µ_ex and PICT are crucial to the enhancement.     

Composition‐ and Shape‐Controlled Synthesis and Optical Properties of ZnxCd1–xS Alloyed Nanocrystals

Composition‐tunable Zn_xCd_1–xS alloyed nanocrystals have been synthesized by a new approach consisting of thermolyzing a mixture of cadmium ethylxanthate (Cd(exan)₂) and zinc ethylxanthate (Zn(exan)₂) precursors in hot, coordinating solvents at relatively low temperatures (180–210 °C). The composition of the alloyed nanocrystals was accurately adjusted by controlling the molar ratio of Cd(exan)₂ to Zn(exan)₂ in the mixed reactants. The alloyed Zn_xCd_1–xS nanocrystals prepared in HDA/TOP (HDA: hexadecylamine; TOP: trioctylphosphine) solution exhibit composition‐dependent shape and phase structures as well as composition‐dependent optical properties. The shape of the Zn_xCd_1–xS nanocrystals changed from dot to single‐armed rod then to multi‐armed rod with a decrease of Zn content in the ternary nanoparticles. The alloying nature of the Zn_xCd_1–xS nanocrystals was consistently confirmed by the results of high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), and UV‐vis absorption and photoluminescence (PL) spectroscopy. Further, the shape‐controlled synthesis of the ternary alloyed nanocrystals was realized by selecting appropriate solvents. Uniform nanodots in the whole composition range were obtained from TOPO/TOP solution, (TOPO: trioctylphosphine oxide) and uniform nanorods in the whole composition range were prepared from HDA/OA solution (OA: octylamine). The effect of the reaction conditions, such as solvent, reaction temperature, and reaction time, on the PL spectra of the alloyed Zn_xCd_1–xS nanocrystals was also systematically studied, and the reaction conditions were optimized for improving the PL properties of the nanocrystals.     

Molecule Charge Transfer Doping for p‐Channel Solution‐Processed Copper Oxide Transistors

The doping of semiconductors plays a critical role in improving the performance of modern electronic devices by precisely controlling the charge carrier density. However, the absence of a stable doping method for p‐type oxide semiconductors has severely restricted the development of metal oxide‐based transparent p–n junctions and complementary circuits. Here, an efficient and stable doping process for p‐type oxide semiconductors by using molecule charge transfer doping with tetrafluoro‐tetracyanoquinodimethane (F₄TCNQ) is reported. The selections of a suitable dopant and geometry play a crucial role in the charge‐transfer doping effect. The insertion of a F₄TCNQ thin dopant film (2–7 nm) between a Au source‐drain electrode and solution‐processed p‐type copper oxide (Cu_xO) film in bottom‐gate top‐contact thin‐film transistors (TFTs) provides a mobility enhancement of over 20‐fold with the desired threshold voltage adjustment. By combining doped p‐type Cu_xO and n‐type indium gallium zinc oxide TFTs, a solution‐processed transparent complementary metal‐oxide semiconductor inverter is demonstrated with a high gain voltage of 50. This novel p‐doping method is expected to accelerate the development of high‐performance and reliable p‐channel oxide transistors and has the potential for widespread applications.