Molecularly Engineered Alicyclic Organic Spacers for 2D/3D Hybrid Tin-based Perovskite Solar Cells.

The high defect density and inferior crystallinity remain great hurdles for developing highly efficient and stable Sn-based perovskite solar cells (PSCs). 2D/3D heterostructures show strong potential to overcome these bottlenecks; however, a limited diversity of organic spacers has hindered further improvement. Herein, a novel alicyclic organic spacer, morpholinium iodide (MPI), is reported for developing structurally stabilized 2D/3D perovskite. Introducing a secondary ammonium and ether group to alicyclic spacers in 2D perovskite enhances its rigidity, which leads to increased hydrogen bonding and intermolecular interaction within 2D perovskite. These strengthened interactions facilitate the formation of highly oriented 2D/3D perovskite with low structural disorder, which leads to effective passivation of Sn and I defects. Consequently, the MP-based PSCs achieved a power conversion efficiency (PCE) of 12.04% with superior operational and oxidative stability. This work presents new insight into the design of organic spacers for highly efficient and stable Sn-based PSCs.

Heterogeneous Nucleation Regulation Amends Unfavorable Crystallization Orientation and Defect Features of Antimony Selenosulfide Film for High-Efficient Planar Solar Cells.

Antimony selenosulfide (Sb2(S,Se)3) has obtained widespread concern for photovoltaic applications as a light absorber due to superior photoelectric features. Accordingly, various deposition technologies have been developed in recent years, especially hydrothermal deposition method, which has achieved a great success. However, device performances are limited with severe carrier recombination, relating to the quality of absorber and interfaces. Herein, bulk and interface defects are simultaneously suppressed by regulating heterogeneous nucleation kinetics with barium dibromide (BaBr2) introduction. In details, the Br adsorbs and dopes on the polar planes of cadmium sulfide (CdS) buffer layer, promoting the exposure of nonpolar planes of CdS, which facilitates the favorable growth of [hk1]-Sb2(S,Se)3 films possessing superior crystallinity and small interface defects. Additionally, the Se/S ratio is increased due to the replacement of S/Se by Br, causing a downshift of the Fermi levels with a benign band alignment and a shallow-level defect. Moreover, Ba2+ is located at grain boundaries by coordination with S and Se ions, passivating grain boundary defects. Consequently, the efficiency is increased from 7.70% to 10.12%. This work opens an avenue towards regulating the heterogeneous nucleation kinetics of Sb2(S,Se)3 film deposited via hydrothermal deposition approach to optimize its crystalline orientation and defect features.

Enhancing Perovskite Solar Cell Performance through Propylamine Hydroiodide Passivation.

In recent years, the power conversion efficiency of perovskite solar cells has increased rapidly. Perovskites can be prepared using simple and cost-effective solution methods. However, the perovskite films obtained are usually polycrystalline and contain numerous defects. Passivation of these defects is crucial for enhancing the performance of solar cells. Here, we report the use of propylamine hydroiodide (PAI) for defect passivation. We found that PAI can result in higher-efficiency cells by reducing the defects and suppressing non-radiative recombination. Consequently, n-i-p perovskite solar cells with a certificated efficiency of 21% were obtained. In addition, PAI exhibited excellent performance in p-i-n devices by serving as a buried interface layer, leading to an improved efficiency of 23%.

Physics and chemistry of nitrogen dioxide (NO2) adsorption on gallium nitride (GaN) surface and its interaction with the yellow-luminescence-associated surface state.

Surface states have been a longstanding and sometimes underestimated problem in gallium nitride (GaN) based devices. The instability caused by surface-charge-trapping in GaN-based transistors is practically the same problem faced by the inventors of the silicon (Si) field effect transistors more than half a century ago. Although in Si this problem was eventually solved by oxygen and hydrogen-based passivation, in GaN, such breakthrough has yet to be made. Apparently, some of this surface charge originates in molecules adsorbed on its surface. Here, it is shown that the charge density associated with the GaN yellow band desorbs upon mild heat treatment in vacuum and re-adsorbs on exposure to the air. Selective exposure of GaN to nitrogen dioxide (NO2) reproduces this surface charge to its original distribution, as does exposure to air. Residual gas analysis of the gases desorbed during heat treatment shows a large concentration of nitric oxide (NO). These observations suggest that selective adsorption of NO2 is responsible for the surface charge that deleteriously affects the electrical properties of GaN. The physics and chemistry of this NO2 adsorption, reported here, may open a new path in the search for passivation to improve GaN device reliability.

Ions-induced Assembly of Perovskite Nanocomposites for Highly Efficient Light-Emitting Diodes with EQE Exceeding 30.

Metal halide perovskites, a cost-effective class of semiconductos, hold great promise for display technologies that demand high-efficiency, color-pure light-emitting diodes (LEDs). Early research on three-dimensional (3D) perovskites showed low radiative efficiencies due to modest exciton binding energies. To inprove luminescence, reducing dimensionality or grain size has been a common approach. However, dividing the perovskite lattice into smaller units may hinder carrier transport, compromising electrical performance. Moreover, the increased surface area introduce additional surface trap states, leading to greater non-radiative recombination. Here, an ions-induced growth method is employed to assembe lattice-anchored perovskite nanocomposites for efficient LEDs with high color purity. This approach enables the nanocomposite thin films, composed of 3D CsPbBr3 and its variant of zero-dimensional (0D) Cs4PbBr6, to feature significant low trap-assisted nonradiative recombination, enhanced light out-coupling with a corrugated surface, and well-balanced charge carrier transport. Based on the resultant 3D/0D perovskite nanocomposites, the perovskite LEDs (PeLEDs) achieving an remarkable external quantum efficiency of 31.0% at the emission peak of 521 nm with a narrow full width at half-maximum of only 18 nm. This sets a new benchmark for color purity in high performance PeLED research, highlighting the significant advantage of this approach.

Metal-N Coordination in Lithium-Sulfur Batteries: Inhibiting Catalyst Passivation.

Lithium-sulfur (Li-S) batteries exhibit great potential as the next-generation energy storage techniques. Application of catalyst is widely adopted to accelerate the redox kinetics of polysulfide conversion reactions and improve battery performance. Although significant attention has been devoted to seeking new catalysts, the problem of catalyst passivation remains underexplored. Herein, we find that metal-N coordination has a previously overlooked role in preventing the catalyst passivation. In the case of nickel, the Ni catalyst reacts with S8 to produce NiSx compounds on the surface, leading to catalyst passivation and slow the kinetics of LiPSs conversion. In contrast, when Ni is coordinated with N (typically Ni-N4), S8 remains stable on the surface. The Ni-N4 exhibits excellent resistance to passivation and rapid kinetics of LiPSs conversion. Consequently, the sulfur cathode with Ni-N4 exhibits a high rate capability of 604.11 mAh g-1 at 3 C and maintains a low capacity decay rate of 0.046% per cycle over 1000 cycles at 2 C. Furthermore, preventing S passivation in M-N coordination applies not only to Ni-N4 but also to various coordination numbers and transition metals. This study reveals a new aspect of metal-N coordination in inhibiting catalyst passivation, improving our understanding of catalysts in Li-S batteries.

Reconstruction and Solidification of Dion-Jacobson Perovskite Top and Buried Interfaces for Efficient and Stable Solar Cells.

Quasi-two-dimensional (Q-2D) perovskites show great potential in the field of photonic and optoelectronic device applications. However, defects and local lattice dislocation still limit performance and stability improvement by nonradiative recombination, unpreferred phase distribution, and unbonded amines. Here, a low-temperature synergistic strategy for both reconstructing and solidifying the perovskite top and buried interface is developed. By post-treating the 1,4-phenylenedimethanammonium (PDMA) based (PDMA)MA4Pb5I16 films with cesium acetate (CsAc) before thermal annealing, a condensation reaction between R-COO- and -NH2 and ion exchange between Cs+ and MA+ occur. It converts the unbonded amines to amides and passivates uncoordinated Pb2+. Meanwhile, it adjusts film composition and improves the phase distribution without changing the out-of-plane grain orientation. Consequently, performance of 18.1% and much-enhanced stability (e.g., stability for photo-oxygen increased over 10 times, light-thermal for T90 over 4 times, and reverse bias over 3 times) of (PDMA)MA4Pb5I16 perovskite solar cells are demonstrated.

Investigations of Crucial Factors for the Non-Covalent Functionalization of Black Phosphorus (BP) using Perylene Diimide Derivatives for the Passivation of BP Nanosheets.

The non-covalent functionalization of black phosphorus (BP) was studied with a scope of ten tailor-made perylene diimides (PDIs). A combination of UV/Vis-, fluorescence-, as well as Raman spectroscopy and atomic force microscopy was used to investigate the structural factors, which contribute to a pronounced PDI-BP interaction and thus support the protection of BP nanosheets against oxidative degradation. We were able to show, that water-soluble, amphiphilic PDIs with highly charged head groups can be used for the non-covalent functionalization of BP in aqueous media. Here, based on the hydrophobic effect, an efficient adsorption of the respective PDI molecules takes place and leads to the formation of a passivating film, yielding a considerable stabilization of the BP flakes under ambient conditions exceeding 30 days.

A brief review of perovskite quantum dot solar cells:Synthesis, property and defect passivation.

Perovskite quantum dot solar cells (PQDSCs), as the promising candidate for the next generation of solar cell, have garnered the significant attention over the past decades. However, the performance and stability of PQDSCs are highly dependent on the properties of interfaces between the perovskite quantum dots (PQDs) and the other layers in the device. This work provides a brief overview of PQDSCs, including the synthesis of PQDs, the characteristics and preparation methods of PQDs, the photoelectric properties as the light absorption layer and optimization methods for PQDSCs with high efficiency. Future directions and potential applications are also highlighted.

Regulating Functional Groups to Construct a Mild Passivator Enhancing the Efficiency and Stability of Carbon-Based Perovskite Solar Cells.

The abundant defects on the perovskite surface greatly impact the efficiency improvement and long-term stability of carbon-based perovskite solar cells. Molecules with electron-donating or electron-withdrawing functional groups have been cited for passivating various defects. However, few studies have investigated the potential adverse effects arising from the synergistic interactions among functional groups. Herein, we investigate the correlation between functional group configurations and passivation strength as well as the potential adverse impacts of strong electrostatic structures by methodically designing three distinct interface molecules functionalized with different ending groups, which both belong to biguanide derivatives, including 1-(3,4-dichlorophenyl) biguanide hydrochloride (DBGCl), metformin hydrochloride (MFCl), and biguanide hydrochloride (BGCl). The results indicate that DBGCl establishes comparatively mild active sites, not only passivates defects but also aids in forming a surface with a uniform potential. Conversely, MFCl exerts a more pronounced adverse effect on the perovskite surface, which is attributable to the electronic state perturbations induced by its functional groups. Due to the lack of hydrophobic groups, devices treated with BGCl demonstrate insufficient moisture resistance. Devices passivated with DBGCl demonstrate superior average efficiency, showcasing a 12% enhancement relative to the pristine. Furthermore, DBGCl-treated devices exhibit enhanced stability in three different environments, respectively, achieving the highest PCE retention rates under nitrogen conditions (25 °C), room-temperature air conditions (25 °C, RH = 40 ± 2%), and high-temperature air conditions (65 °C, RH = 40 ± 2%).

Regulation of Lead Iodide Crystallization and Distribution for Efficient Perovskite Solar Cells.

At present, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached 26.1%. Polycrystalline perovskite films prepared by sequential deposition are often accompanied by excess PbI2. Although excess PbI2 can reduce the internal defects of the perovskites and promote charge transfer, excess PbI2 is unevenly distributed in the perovskites and easily decomposed into the composite center of charge. Therefore, the growth and distribution of PbI2 crystals can be regulated by introducing 4-fluoroaniline (4-FLA) as an additive into the precursor of PbI2. We observe that the presence of an amino group in 4-FLA leads to a reduction in the strength of van der Waals forces between PbI2 layer structures, thereby facilitating the uniform dispersion of excess PbI2 within the perovskites. Additionally, 4-FLA is restricted from being embedded in the PbI2 layer due to the steric hindrance of 4-FLA and the hydrogen bond interaction between nitrogen atoms and PbI2. Therefore, it leads to better dispersion of PbI2, resulting in better passivation and device efficiency. Based on the hydrophobicity of the benzene ring, the modified perovskite film shows excellent hydrophobicity. Ultimately, we achieved 21.63% PCE and 1.16V VOC. This provides an effective strategy for regulating excess PbI2 to achieve efficient and stable PSCs.

Interface Engineering by Unsubstituted Pristine Nickel Phthalocyanine as Hole Transport Material for Efficient and Stable Perovskite Solar Cells.

Lead halide perovskite solar cells (PSCs) have been rapidly developed in the past decade. With the development of a PSC, interface engineering plays an increasingly important role in maximizing device performance and long-term stability. We report a simple and effective interface engineering method for achieving improvement of PSCs up to 20% by employing unsubstituted pristine nickel phthalocyanine (NiPc). Thermal annealing of NiPc improves the interface between NiPc and perovskite because of the incorporation of NiPc molecules into the perovskite grain boundaries, which creates improvements in hole extraction from the perovskite absorber layer, as evidenced by time-resolved photoluminescence measurements. This significantly improves the charge transfer and collection efficiency, which are closely related to the improvement of the interface between perovskite and NiPc.

Efficient Perovskite Solar Cells by Employing Triphenylamine-Functionalized Azadipyrromethene Dyes as Dopant-Free Hole-Transporting Materials and Bidentate Surface Passivating Agents.

In this study, a series of dopant-free, low-cost hole-transporting materials (HTMs) based on triphenylamine-functionalized azadipyrromethene dyes 1-3 (TPA-ADPs 1-3) were designed and synthesized. The properties of these new HTMs were investigated by optical spectroscopy, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetric, atomic force microscopy, and X-ray diffraction, as well as theoretical calculations. The results indicated that the TPA-ADPs 1-3 presented well-matched energy levels with perovskite, higher hole mobility, as well as more effective defect passivation at the perovskite/HTM interface by the coordination interaction between the ADP moiety and the undercoordinated Pb2+. The n-i-p perovskite solar cells (PSCs) employing HTMs 1-3 as well as doped Spiro-OMeTAD were fabricated and characterized. The TPA-ADP 1-based PSCs exhibited the best performance with a champion power conversion efficiency (PCE) of 22.13% and an fill factor of 0.81, which was superior to that of the devices based on the doped Spiro-OMeTAD. Long-term device performance studies indicated that the TPA-ADP 1-based PSCs maintained 80% of the initial PCE after 1800 h of storage in the ambient condition of 40-60% RH, which was also higher than the stability of doped Spiro-OMeTAD-based devices under the same conditions.

Enhanced Performance and Stability of Perovskite Solar Cells Through Surface Modification with Benzocaine Hydrochloride.

Current development of inverted p-i-n perovskite solar cells (PSCs), with nickel oxide as the hole transport layer, is progressing toward lower net costs, higher efficiencies, and superior stabilities. Unfortunately, the high density of defect-based traps on the surface of perovskite films significantly limits the photoelectric conversion efficiency and operational stability of perovskite solar cells. Finding cost-effective interface modifiers is crucial for the further commercial development of p-i-n PSCs. In the present work, we report a passivation strategy using a multifunctional molecule, benzocaine hydrochloride (BHC), which is shown to reduce defect density and enhance the photovoltaic performance and stability of the resultant p-i-n PSCs. It has been revealed that BHC strongly interacts with perovskite precursor components and triggers the evolution of the perovskite absorber film morphology and enables improved surface energy level alignment, thus promoting charge carrier transport and extraction. These properties are beneficial for improving open-circuit voltage (VOC) and fill factor (FF). Our results show that the photoelectric conversion efficiency (PCE) of p-i-n PSCs with nickel oxide as the hole transport layer increased from an initial 20.0% to 22.1% after being passivated with BHC, and these passivated devices also exhibited improved stability. DFT calculations reveal the unusual ability of the BHC passivant to improve band alignment while also preventing the accumulation of holes at the interface. In this work, the advantages of BHC passivation are demonstrated by linking theoretical calculations with optical and electrical characterizations.

Sustainable Cr(VI) reduction in a membrane-less TPBC-MFC driven by solid watermelon rind.

Sustainable Cr(VI) reduction by microbial fuel cell (MFC) is a major challenge due to the electrode passivation and available electron donors. In this study, the chromate removal across a period of more than three months in a membrane-less TPBC-MFC with solid watermelon rind (SWMR) as electron donors was investigated. The TPBC benefited the Cr(VI) reduction and voltage output owing to the enhanced mass transfer. The average Cr(VI) removal efficiency (RE) of 97%, effluent COD of 80 mg/L and voltage output of 130 mV were achieved during the long-term operation on the TPBC-MFC. The SEM-EDS analysis showed that all biofilms were predominated by rod- and coccus-shaped bacteria and the Cr(VI) reduction was mainly carried out by the S-cathode. The XPS, XRD and FT-IR analysis revealed that the major product of cathodic Cr(VI) reduction was a Cr(III) precipitate in the form of Cr(OH)3. Microbial community structure disclosed that fermentation microorganisms (e.g. Anaeroarcus) and electroactive bacteria (e.g. Porphyromonadaceae) jointly responsible for SWMR degradation and electricity generation were dominant at the anode, while the chromate-associated microorganisms (e.g. Comamonadaceae and Cloacibacterium) dominated at the cathode. The biofilms adsorbing Cr(OH)3 precipitates fell off from the cathode periodically to avoid the passivation. Overall, our study suggests a really sustainable approach with which a goal of simultaneously reusing watermelon rind, reducing Cr(VI) and producing electricity was attained perfectly.

Surface Property Regulation of a Magnetron-Sputtered NiOx Hole Transport Layer for High-Performance Inverted Perovskite Solar Cells.

The inverted perovskite solar cells (PSCs) are gaining increasing attention recently for their unprecedented advantages, such as better integration with tandem and flexible designs, negligible hysteresis, good operational stability, and compatibility with commercially scalable fabrication approaches. Nickel oxide (NiOx) films prepared by magnetron sputtering technology exhibit excellent scalability and reproducibility, which could well meet the requirements of the large-scale production of inverted PSCs. However, NiOx prepared by vacuum methods generally has fewer surface hydroxyl groups, deteriorating the wettability and damaging the interface contact with the perovskite. Particularly, the Ni3+ defects on the NiOx surface could lead to unfavorable redox reactions with organic cations in the perovskite under high temperatures, promoting the rapid degradation of the perovskite. Thus, surface regulation of sputtered NiOx is imperative for high-performance PSCs. Herein, 4-(trifluoromethyl) phenylcarbamate hydrochloride (TFFA) was used to regulate the surface properties of sputtered NiOx. The strongly electronegative F ions in TFFA passivated the Ni3+ defects on the NiOx surface, suppressed unfavorable interface reactions, and improved charge recombination. The polar ammonium functional group was used to adjust the surface energy of NiOx, thereby improving the wettability and optimizing the crystallization kinetics of the perovskite. As a result, the power conversion efficiency (PCE) of PSCs reached 22.76%, which was among the highest PCEs reported for sputtered NiOx-based inverted PSCs to date. Moreover, the unencapsulated target devices exhibited better stability, maintaining over 85% of the initial PCE after aging for approximately 1200 h in a N2 environment. Our achievements pointed out a practical strategy for enhancing the performance of sputtered NiOx-based inverted PSCs, which could potentially accelerate the development and application of large-area PSCs.

Dual Modification Strategy: Passivation Layer and Cocatalyst on Hematite for Improved Photoelectrochemical Water Oxidation.

α-Fe2O3 is a very attractive photoanode for photoelectrochemical (PEC) water decomposition. However, its short diffusion length, poor conductivity, and fast charge-carrier recombination severely limit device efficiency. Here, coloading an Al2O3 passivation layer and a CoOx cocatalyst onto Ti-doped α-Fe2O3 was carried out to promote PEC water oxidation by improving charge separation and transfer at the electrode/electrolyte interface and inhibiting photocarrier recombination. The optimized Ti:Fe2O3/Al2O3/CoOx photoanode shows a large photocurrent density of 1.41 mA cm-2 at 1.23 V vs reversible hydrogen electrode, which is 47 times greater than that of a pristine Ti:Fe2O3 photoanode. The dual modifications with a combined passivation layer and cocatalyst on the photoanode verify a valuable way for solar energy conversion in PEC water oxidation.

Operational Characteristics of AlGaN/GaN High-Electron-Mobility Transistors with Various Dielectric Passivation Structures for High-Power and High-Frequency Operations: A Simulation Study.

This study investigates the operational characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) by employing various passivation materials with different dielectric constants and passivation structures. To ensure the simulation reliability, the parameters were calibrated based on the measured data from the fabricated basic Si3N4 passivation structure of the HEMT. The Si3N4 passivation material was replaced with high-k materials, such as Al2O3 and HfO2, to improve the breakdown voltage. The Al2O3 and HfO2 passivation structures achieved breakdown voltage improvements of 6.62% and 17.45%, respectively, compared to the basic Si3N4 passivation structure. However, the increased parasitic capacitances reduced the cut-off frequency. To mitigate this reduction, the operational characteristics of hybrid and partial passivation structures were analyzed. Compared with the HfO2 passivation structure, the HfO2 partial passivation structure exhibited a 7.6% reduction in breakdown voltage but a substantial 82.76% increase in cut-off frequency. In addition, the HfO2 partial passivation structure exhibited the highest Johnson's figure of merit. Consequently, considering the trade-off relationship between breakdown voltage and frequency characteristics, the HfO2 partial passivation structure emerged as a promising candidate for high-power and high-frequency AlGaN/GaN HEMT applications.

De-Passivation and Surface Crystal Plane Reconstruction via Chemical Polishing for Highly Reversible Zinc Anodes.

Despite the widespread adoption of Zn anodes for aqueous energy storage, the presence of an inherent passivation layer and the polycrystalline interface of commercial Zn foil consistently lead to non-uniform electrodeposition, undermining stability and practicality. Herein, the study introduces a chemically polished Zn metal anode (CP-Zn) fabricated via a simple immersion method. This "chemically polishing" process can effectively remove the interfacial passivation layer (de-passivation), providing ample active sites for plating/stripping and ensuring the uniformly distributed electric field and Zn2+ ion flux. Additionally, selective etching during chemical polishing exposes more (002) crystal planes, promoting homogeneous and smooth zinc deposition while suppressing related side reactions. Demonstrated by CP-Zn anode, the symmetric cell exhibits stable cycling over 4600 h at 1 mA cm-2 and 240 h at 50% depth of discharge (DOD), with a CP-Zn||VO2 full cell maintaining ≈75.3% capacity retention over 1000 cycles at 3 A g-1. This chemically polishing strategy presents a promising avenue for advancing the commercialization of aqueous zinc-ion batteries.

Innovative In Situ Passivation Strategy for High-Efficiency Sb2(S,Se)3 Solar Cells.

An effective defect passivation strategy is crucial for enhancing the performance of antimony selenosulfide (Sb2(S,Se)3) solar cells, as it significantly influences charge transport and extraction efficiency. Herein, a convenient and novel in situ passivation (ISP) technique is successfully introduced to enhance the performance of Sb2(S,Se)3 solar cells, achieving a champion efficiency of 10.81%, which is among the highest recorded for Sb2(S,Se)3 solar cells to date. The first principles calculations and the experimental data reveal that incorporating sodium selenosulfate in the ISP strategy effectively functions as an in situ selenization, effectively passivating deep-level cation antisite SbSe defect within the Sb2(S,Se)3 films and significantly suppressing non-radiative recombination in the devices. Space-charge-limited current (SCLC), photoluminescence (PL), and transient absorption spectroscopy (TAS) measurements verify the high quality of the passivated films, showing fewer traps and defects. Moreover, the ISP strategy improved the overall quality of the Sb2(S,Se)3 films, and fine-tuned the energy levels, thereby facilitating enhanced carrier transport. This study thus provides a straightforward and effective method for passivating deep-level defects in Sb2(S,Se)3 solar cells.