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The bottom perovskite with the hole transport layer (HTL) in inverted perovskite solar cells (PSCs) interface has received little attention due to challenges like interlayer dissolution during perovskite deposition. And voids at the perovskite/HTL interface can degrade cell performance. This work introduces a two‐dimensional (2D) perovskite layer between the perovskite and poly (N, N′‐bis‐4‐butylphenyl‐N, N′‐bisphenyl) benzidine (Poly‐TPD) HTL using a mixed solution of 4‐methylphenethylammonium chloride (4M‐PEA‐Cl), methylammonium iodide (MA‐I), and Poly(9,9‐bis(3′‐(N,N‐dimethyl)‐N‐ethylammoinium‐propyl‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene))dibromide (PFN‐Br). The amine functional groups in the organic salts improved HTL wettability, resulting in a void‐free interface. 4M‐PEA‐Cl, with its strong electron‐withdrawing benzene ring, outperformed other amine‐containing salts in passivating undercoordinated Pb2+ ions. Incorporating this hybrid passivation layer in PSCs resulted in a 1.8% absolute increase in power conversion efficiency (PCE) to 19.1% with 1.68 eV perovskite bandgap. Additionally, the passivated PSCs demonstrated enhanced operational stability, retaining 91% of their initial efficiency after 800 hours of continuous 1‐sun illumination, compared to 84.7% for the control sample. [ABSTRACT FROM AUTHOR]

Crucial advancements in versatile catalyst systems capable of achieving high current densities under industrial conditions, bridging the gap between fundamental understanding and practical applications, are pivotal to propel the hydrogen economy forward. In this study, vertically oriented hierarchically multiscale nanoflakes of NiFeCo electrocatalysts are presented, developed by surface modification of a porous substrate with nano‐structured nickel. The resulting electrodes achieve remarkably low overpotentials of 139 mV at 10 mAcm−2 and 248 mV at 500 mAcm−2. Further, scaled‐up electrodes are implemented in a water‐splitting electrolyser device exhibiting a stable voltage of 1.82 V to deliver a constant current density of 500 mA cm−2 for over 17 days. Moreover, the role of the unique structures on electrochemical activity is systematically investigated by fractal analysis, involving computation of structure factors such as Minkowski connectivity, fractal dimension, and porosity using scanning electron microscope images. It is found that such structures offer higher surface area than typical layered double hydroxide structures due to morphological coherence that results in a superhydrophilic surface, while the base Ni layer boosts the charge transfer. This study demonstrates a Ni/NiFeCo(OH)x heterostructure with highly porous morphology, a key to unlocking extremely efficient oxygen evolution reaction activity with exceptional stability. Moreover, fractal analysis is presented as a valuable tool to evaluate the electrochemical performance of catalysts for their structured morphology. [ABSTRACT FROM AUTHOR]

A scalable growth of atomically‐thin 2D transition metal dichalcogenides (TMDs) with defect‐free large‐area surfaces is crucial for developing high‐performing optoelectronic devices. Herein, a method to grow large‐area, high‐quality MoSe2 monolayers, MoSe2–WSe2, and WSe2–MoSe2 lateral heterostructures using molten salt‐based chemical vapor deposition (CVD) is systematically reported. First, effects of isolated inorganic (sodium chloride (NaCl) and sodium nitrate (NaNO3)), organic (Perylene–3,4,9,10–tetracarboxylic acid tetrapotassium salt (PTAS), mixed inorganic (NaCl/NaNO3), and hybrid organic–inorganic (PTAS/NaCl/NaNO3) salt catalysts on the CVD growth and optoelectronic quality of MoSe2 monolayers and their lateral heterostructures with WSe2 in MoSe2–WSe2 and WSe2–MoSe2 assemblies are investigated. Results show that molten salt catalysts (NaCl/NaNO3 and PTAS/NaCl/NaNO3) support high‐quality, large‐area growth of MoSe2 monolayers with low defect density. The mixed inorganic salt supports growth of MoSe2–WSe2 lateral heterostructures but not their counterpart. Meanwhile, WSe2–MoSe2 lateral heterostructures are optimally grown, supported by the hybrid organic–inorganic salt. These results are ascribed to the difference in the associated kinetic and thermodynamic mechanisms for the growths of MoSe2 and WSe2 as starting materials. Last, it is confirmed that optoelectronic quality of realized heterostructures and monolayers is improved compared to their mechanically exfoliated counterparts. The obtained high‐quality, large‐area 2D TMD heterostructures can be useful for various optoelectronic applications. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive study regarding the impact of the Al electrode on the surface passivation of three TiOx‐based passivating selective contacts: TiOx:Al/LiFx/Al,TiOx/LiFx/Al, and a‐Si/TiOx:Al/LiFx/Al. A deterioration in passivation is recorded after the deposition of the Al electrode at close to room temperature, where the deterioration correlated to the Al thickness. A thin Al (10 nm) electrode resulted in the most severe passivation decline, while samples with a 100 nm Al electrode showed much less passivation deterioration. Furthermore, it is found that a low‐temperature annealing step led to a partial recovery of the passivation, particularly in the case of TiOx:Al/LiFx/Al and a‐Si/TiOx:Al/LiFx/Al contacts. The presented discovery in this article provides crucial insight into the importance of characterization and evaluation of passivating contacts, which is demonstrated here to be highly sensitive to the deposited metal thickness and the interfacial layers, as well as to the post‐deposition annealing. [ABSTRACT FROM AUTHOR]

Passivating contacts based on transition metal oxides (TMOs) have the potential to overcome existing performance limitations in high‐efficiency crystalline silicon (c‐Si) solar cells, which is a significant driver for continuing cost/Watt reductions of photovoltaic electricity. Herein, innovative stacks of Al‐alloyed TiOx (AlyTiOx) and pure TiOx as transparent electron‐selective passivating contacts for n‐type c‐Si surfaces are explored. An optimized stack of 2 nm AlyTiOx and 2 nm TiOx is shown to provide both record‐quality surface passivation and excellent electrical contact, with a surface recombination current density prefactor J0 of 2.4 fA cm−2 and a specific contact resistivity ρc of 15.2 mΩ cm2. The performance of this innovative stack significantly exceeds previously reported values for pure or doped TiOx single layers, SiOx/TiOx stacks, a‐Si:H/TiOx stacks, and other transparent contact technologies. Furthermore, an excellent efficiency of 21.9% is attained by incorporating the optimized stack as a full‐area rear contact in an n‐type c‐Si solar cell. The findings set a new benchmark for the passivation performance of metal oxide‐based passivating contacts, bringing it to a level on par with state‐of‐the‐art SiOx/poly‐Si contacts while greatly improving optical transparency. [ABSTRACT FROM AUTHOR]

Nonpolar m-plane AlGaN offers the advantage of polarization-free multiple quantum wells (MQWs) for ultraviolet (UV) emission and can be achieved on the sidewalls of selective area grown GaN nanowires. We reveal that the growth of AlGaN on GaN nanowires by metal organic chemical vapor deposition (MOCVD) is driven by vapor-phase diffusion, and consequently puts a limit on the pitch of nanowire array due to shadowing effect. An insight into the difficulty of achieving metal-polar AlGaN nanowire by selective area growth (SAG) in MOCVD is also provided and can be attributed to the strong tendency to form pyramidal structure due to a very small growth rate of { 10 1 ¯ 1 } semipolar planes compared to (0001) c-plane. The nonpolar m-plane sidewalls of GaN nanowires obtained via SAG provides an excellent platform for growth of nonpolar AlGaN MQWs. UV emission from m-plane AlxGa1−xN/AlyGa1−yN MQWs grown on sidewalls of dislocation-free GaN nanowire is demonstrated in the wavelength range of 318–343 nm. [ABSTRACT FROM AUTHOR]

We show that ZnMoO4 remains in stable phase under thermal annealing up to 1000 °C, whereas it decomposes to ZnO and MoO3 under transient thermal spike induced by 100MeV Ag irradiation. The transformation is evidenced by X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Thin films of ZnMoO4 were synthesized by thermal evaporation and subsequent annealing in oxygen ambient at 600 °C for 4 h. XRD results show that as the irradiation fluence increases, the peak related to ZnMoO4 decreases gradually and eventually disappear, whereas peaks related to ZnO grow steadily up to fluence of 3×1012 ions/cm² and thereafter remain stable till highest fluence. This indicates that polycrystalline ZnMoO4 film has transformed to polycrystalline ZnO thin film. The Raman lines related to ZnMoO4 are observed to have disappeared with increasing irradiation fluence. XPS results show modification in bonding and depletion of Mo from near surface region after the ion irradiation. Cross-sectional transmission electron microscopy result shows the formation of ion track of diameter 12-16 nm. These results demonstrate that ion beam methods provide the means to control phase splitting of ZnMoO4 to ZnO and MoO3 within nanometric dimension along the ion track. The observation of phase splitting and Mo loss are explained in the framework of ion beam induced thermal spike formalism. [ABSTRACT FROM AUTHOR]

The bulk photovoltaic (BPV) effect of conventional ferroelectric (FE) materials has sparked a great deal of interest due to anomalous above-bandgap photovoltage. However, large bandgaps and weak photocurrents remain longstanding challenges for FE PV materials in practical applications. To address these issues, we propose a new defect-engineering strategy and demonstrate it on a narrow bandgap centrosymmetric material, BiNbO4 (BNO): the BPV effect is introduced into BNO by tuning the defect amounts, then a defect-modified homojunction structure is constructed to enhance the BPV effect. This defect engineering strategy enables synergetic effects, e.g., enhanced light absorption, FE-like depolarization field and interfacial polarization. This homojunction structure results in two-fold promotion of photovoltage and ten-fold promotion of photocurrent, compared to the defect-modified BNO sample. We believe this new strategy will break through limitations in traditional material design and pave a novel route to future multifunctional materials, especially high performance BPV materials. [ABSTRACT FROM AUTHOR]