Explore the vast range of titles available.

Colloidal CsPbX3 (X = Br, Cl, and I) perovskite nanocrystals exhibit tunable bandgaps over the entire visible spectrum and high photoluminescence quantum yields in the green and red regions. However, the lack of highly efficient blue‐emitting perovskite nanocrystals limits their development for optoelectronic applications. Herein, neodymium (III) (Nd3+) doped CsPbBr3 nanocrystals are prepared through the ligand‐assisted reprecipitation method at room temperature with tunable photoemission from green to deep blue. A blue‐emitting nanocrystal with a central wavelength at 459 nm, an exceptionally high photoluminescence quantum yield of 90%, and a spectral width of 19 nm is achieved. First principles calculations reveal that the increase in photoluminescence quantum yield upon doping is driven by an enhancement of the exciton binding energy due to increased electron and hole effective masses and an increase in oscillator strength due to shortening of the PbBr bond. Putting these results together, an all‐perovskite white light‐emitting diode is successfully fabricated, demonstrating that B‐site composition engineering is a reliable strategy to further exploit the perovskite family for wider optoelectronic applications. Narrowband blue‐emitting CsPbBr3 perovskite nanocrystals with a photoluminescence quantum yield of 90% are achieved by B‐site doping of neodymium ions. The doping concentration can tune the emission spectrum in a controlled manner. First principles calculations reveal that dopant‐induced electronic changes dominate the bandgap tunability and the high quantum yield is associated with enhanced exciton binding energy and oscillator strength.

SignificanceSurface states of topological insulators (TIs) should exhibit extraordinary electronic phenomena when a ‘Dirac-mass gap’ is opened in their spectrum, typically by creating a ferromagnetic state. However, our direct visualization of the Dirac-mass gap Δ(r) in a ferromagnetic TI reveals its intense disorder at the nanoscale. This is correlated with the density of magnetic dopant atoms n(r), such that Δ(r)∝n(r) as anticipated for surface-state–mediated ferromagnetism. Consequent new perspectives on ferromagnetic TI physics include that the quantum anomalous Hall effect occurs in this environment of extreme Dirac-mass disorder and that paths of associated chiral edge states must be tortuous. To achieve all the exotic physics expected of ferromagnetic TIs, greatly improved control of dopant-induced Dirac-mass gap disorder is therefore required. To achieve and use the most exotic electronic phenomena predicted for the surface states of 3D topological insulators (TIs), it is necessary to open a “Dirac-mass gap” in their spectrum by breaking time-reversal symmetry. Use of magnetic dopant atoms to generate a ferromagnetic state is the most widely applied approach. However, it is unknown how the spatial arrangements of the magnetic dopant atoms influence the Dirac-mass gap at the atomic scale or, conversely, whether the ferromagnetic interactions between dopant atoms are influenced by the topological surface states. Here we image the locations of the magnetic (Cr) dopant atoms in the ferromagnetic TI Cr0.08(Bi0.1Sb0.9)1.92Te3. Simultaneous visualization of the Dirac-mass gap Δ(r) reveals its intense disorder, which we demonstrate is directly related to fluctuations in n(r), the Cr atom areal density in the termination layer. We find the relationship of surface-state Fermi wavevectors to the anisotropic structure of Δ(r) not inconsistent with predictions for surface ferromagnetism mediated by those states. Moreover, despite the intense Dirac-mass disorder, the anticipated relationship Δ(r)∝n(r) is confirmed throughout and exhibits an electron–dopant interaction energy J* = 145 meV·nm2. These observations reveal how magnetic dopant atoms actually generate the TI mass gap locally and that, to achieve the novel physics expected of time-reversal symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential.

Designing highly durable and active electrocatalysts applied in polymer electrolyte membrane (PEM) electrolyzer for the oxygen evolution reaction remains a grand challenge due to the high dissolution of catalysts in acidic electrolyte. Hindering formation of oxygen vacancies by tuning the electronic structure of catalysts to improve the durability and activity in acidic electrolyte was theoretically effective but rarely reported. Herein we demonstrated rationally tuning electronic structure of RuO 2 with introducing W and Er, which significantly increased oxygen vacancy formation energy. The representative W 0.2 Er 0.1 Ru 0.7 O 2-δ required a super-low overpotential of 168 mV (10 mA cm − 2 ) accompanied with a record stability of 500 h in acidic electrolyte. More remarkably, it could operate steadily for 120 h (100 mA cm − 2 ) in PEM device. Density functional theory calculations revealed co-doping of W and Er tuned electronic structure of RuO 2 by charge redistribution, which significantly prohibited formation of soluble Ru x>4 and lowered adsorption energies for oxygen intermediates. There is an increasing interest in understanding how defect chemistry can alter material reactivity. Here, authors tune the electronic structure of RuO 2 by introducing W and Er dopants that boost acidic oxygen evolution performances by limiting oxygen vacancy formation during catalysis.

The evolution of the contact scheme has driven the technology revolution of crystalline silicon (c‐Si) solar cells. The state‐of‐the‐art high‐efficiency c‐Si solar cells such as silicon heterojunction (SHJ) and tunnel oxide passivated contact (TOPCon) solar cells are featured with passivating contacts based on doped Si thin films, which induce parasitic optical absorption loss and require capital‐intensive deposition processes involving flammable and toxic gasses. A promising solution to tackle this problem is to employ dopant‐free passivating contact, involving the use of transparent and cost‐effective wide band gap materials. In this review, we first introduce the dopant‐free passivating contact, from carrier transport mechanisms, material classification to evaluation methods. Then we focus on the advances in different strategies to improve cell performance, including material property optimization, structural and interfacial engineering, as well as various post‐treatments. At the end, the challenge and perspective of dopant‐free passivating contact c‐Si solar cells are discussed. This article provides an overview of the mechanism and materials of dopant‐free passivating contacts for crystalline silicon solar cells, and focuses on the recent advances in contact configuration and interface engineering for efficiency and stability enhancement.

Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices 1 – 9 . N(electron)-doping is fundamentally more challenging than p(hole)-doping and typically achieves a very low doping efficiency ( η ) of less than 10% 1 , 10 . An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability 1 , 5 , 6 , 9 , 11 , which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal (for example, Pt, Au, Pd) as vapour-deposited nanoparticles or solution-processable organometallic complexes (for example, Pd 2 (dba) 3 ) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling greatly increased η in a much shorter doping time and high electrical conductivities (above 100 S cm −1 ; ref. 12 ). This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants and semiconductors, thus opening new opportunities in n-doping research and applications 12 , 13 . Electron doping of organic semiconductors is typically inefficient, but here a precursor molecular dopant is used to deliver higher n-doping efficiency in a much shorter doping time.

Acidic CO 2 -to-HCOOH electrolysis represents a sustainable route for value-added CO 2 transformations. However, competing hydrogen evolution reaction (HER) in acid remains a great challenge for selective CO 2 -to-HCOOH production, especially in industrial-level current densities. Main group metal sulfides derived S-doped metals have demonstrated enhanced CO 2 -to-HCOOH selectivity in alkaline and neutral media by suppressing HER and tuning CO 2 reduction intermediates. Yet stabilizing these derived sulfur dopants on metal surfaces at large reductive potentials for industrial-level HCOOH production is still challenging in acidic medium. Herein, we report a phase-engineered tin sulfide pre-catalyst (π-SnS) with uniform rhombic dodecahedron structure that can derive metallic Sn catalyst with stabilized sulfur dopants for selective acidic CO 2 -to-HCOOH electrolysis at industrial-level current densities. In situ characterizations and theoretical calculations reveal the π-SnS has stronger intrinsic Sn-S binding strength than the conventional phase, facilitating the stabilization of residual sulfur species in the Sn subsurface. These dopants effectively modulate the CO 2 RR intermediates coverage in acidic medium by enhancing *OCHO intermediate adsorption and weakening *H binding. As a result, the derived catalyst (Sn(S)-H) demonstrates significantly high Faradaic efficiency (92.15 %) and carbon efficiency (36.43 %) to HCOOH at industrial current densities (up to −1 A cm −2 ) in acidic medium. Stabilizing sulfur dopants on metal surfaces is important but challenging in acidic CO 2 to HCOOH electrolysis, especially under high current densities. Here the authors present phase engineered SnS pre-catalyst with stronger intrinsic Sn-S binding strength for CO 2 conversion to HCOOH at > 1 A cm −2 in acidic medium.

Heteroatom-doping is a practical means to boost RuO 2 for acidic oxygen evolution reaction (OER). However, a major drawback is conventional dopants have static electron redistribution. Here, we report that Re dopants in Re 0.06 Ru 0.94 O 2 undergo a dynamic electron accepting-donating that adaptively boosts activity and stability, which is different from conventional dopants with static dopant electron redistribution. We show Re dopants during OER, (1) accept electrons at the on-site potential to activate Ru site, and (2) donate electrons back at large overpotential and prevent Ru dissolution. We confirm via in situ characterizations and first-principle computation that the dynamic electron-interaction between Re and Ru facilitates the adsorbate evolution mechanism and lowers adsorption energies for oxygen intermediates to boost activity and stability of Re 0.06 Ru 0.94 O 2 . We demonstrate a high mass activity of 500 A g cata. −1 (7811 A g Re-Ru −1 ) and a high stability number of S-number = 4.0 × 10 6  n oxygen  n Ru −1 to outperform most electrocatalysts. We conclude that dynamic dopants can be used to boost activity and stability of active sites and therefore guide the design of adaptive electrocatalysts for clean energy conversions. RuO 2 is a promising anode catalyst for proton exchange membrane water electrolyzers but suffers from poor catalytic stability. Here the authors present a rhenium-doped RuO 2 with a unique dynamic electron accepting-donating that adaptively boosts activity and stability in acidic water oxidation.

Perovskite solar cells (PSCs) are among the most promising photovoltaic technologies owing to their exceptional optoelectronic properties 1 , 2 . However, the lower efficiency, poor stability and reproducibility issues of large-area PSCs compared with laboratory-scale PSCs are notable drawbacks that hinder their commercialization 3 . Here we report a synergistic dopant-additive combination strategy using methylammonium chloride (MACl) as the dopant and a Lewis-basic ionic-liquid additive, 1,3-bis(cyanomethyl)imidazolium chloride ([Bcmim]Cl). This strategy effectively inhibits the degradation of the perovskite precursor solution (PPS), suppresses the aggregation of MACl and results in phase-homogeneous and stable perovskite films with high crystallinity and fewer defects. This approach enabled the fabrication of perovskite solar modules (PSMs) that achieved a certified efficiency of 23.30% and ultimately stabilized at 22.97% over a 27.22-cm 2 aperture area, marking the highest certified PSM performance. Furthermore, the PSMs showed long-term operational stability, maintaining 94.66% of the initial efficiency after 1,000 h under continuous one-sun illumination at room temperature. The interaction between [Bcmim]Cl and MACl was extensively studied to unravel the mechanism leading to an enhancement of device properties. Our approach holds substantial promise for bridging the benchtop-to-rooftop gap and advancing the production and commercialization of large-area perovskite photovoltaics. A synergistic dopant-additive combination strategy using methylammonium chloride as the dopant and a Lewis-basic ionic-liquid additive is shown to enable the fabrication of perovskite solar modules achieving record certified performance and long-term operational stability.

This work involved the synthesis of compositions of Ba 0.95 Ca 0.05 Sn x Ti 1-x O 3 (BCST) with varying amounts of Sn dopant (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1). A standard solid-state reaction approach was used to create all of the ceramic compounds. Each BCST composite’s microstructure, sintering, morphology, density, optical, and electrical characteristics were carefully examined, and the dielectric performance was optimized. In comparison to the unmodified composite, introducing varied amounts of Sn material into the BCST compound changed the crystal lattice vibrations and functional group locations. This result indicates that there are some variations in unit cell size, revealing that Sn +4 ions diffused effectively inside the lattice structure to produce BSCT composites. Further, SEM micrographs indicated proportionate changes in the homogenous structure and irregular forms as Sn concentration increased, as well as some variation in average grain size. As a consequence, by adding 0.08 mol% of Sn dopant, the crystallite size and average grain size were adjusted to 45.69 nm and 0.66 µm, respectively. Meanwhile, the 0.08-Sn specimen displayed a dielectric constant (Ɛ) with an optimum value of 5557 and a relative decrease in the Curie-Weiss constant. These results are attributed to the existence of various concentrations of Sn ions at the Ti-site of the BCT, which resulted in a compositionally disordered state. This disordered condition is essential for the production of dielectric compounds. Therefore, it is evident that modifying the amount of Sn doping added significantly enhanced the dielectric characteristics of the BCST composites created in this work. However, excessive Sn doping reduces the dielectric properties due to a reduction in tetragonal phase and an increase of disorders and charge fluctuations. Graphical Abstract Highlights Synthesis and characterization of Ba 0.95 Ca 0.05 Sn x Ti 1-x O 3 (BCST) compositions with varying amounts of Sn dopant. A standard solid-state reaction approach was used to create all of the ceramic compounds. The dielectric characteristics of the BCST proved to be highly dependent on the amount of Sn doping employed.

CdZnTe (CZT) ingots doped with different concentrations of indium (2 ppm, 5 ppm, 8 ppm, and 11 ppm) were grown by the Vertical Bridgman Method. The charge transport behaviors of CZT wafers were characterized by Thermally Stimulated Current (TSC), Time of Flight technique (TOF) and Current–Voltage measurements (I–V). TSC results indicate that the concentration of deep donor defects \\[ {\\hbox{Te}}_{\\rm{Cd}}^{{ 2 { + }}} \\] is reduced significantly by increasing indium dopant content from 2 ppm to 8 ppm, while that of indium related traps, \\[ {\\hbox{In}}_{\\rm{Cd}}^{ + } \\] and A-centers, is sharply increased. Hecht fitting and TOF results indicate that the electron mobility keeps nearly unchanged for different dopant concentrations in the region between 2 ppm and 5 ppm, but the lifetime increased greatly with increasing indium dopant concentration. Therefore, (μτ)e value was increased with higher indium dopant. The up-shift of Fermi level is also observed in the temperature-dependent I–V result with the increasing of indium dopant content. Large Schottky barriers are found in detectors with higher indium concentration. High voltage x-ray response results show that the channel number shifts to the low energy side for 2 ppm dopant samples compared with best performance 5 ppm dopant samples, while the full-energy peaks are broadened for 8 ppm and 11 ppm dopant samples.