Dopant-additive synergism enhances perovskite solar modules.

Perovskite solar cells (PSCs) are among the most promising photovoltaic technologies owing to their exceptional optoelectronic properties1,2. However, the lower efficiency, poor stability and reproducibility issues of large-area PSCs compared with laboratory-scale PSCs are notable drawbacks that hinder their commercialization3. 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-cm2 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.

Electrochemically Induced Phase Transformation in Vanadium Oxide Boosts Zn-Ion Intercalation.

Vanadium oxides are excellent cathode materials with large storage capacities for aqueous zinc-ion batteries, but their further development has been hampered by their low electronic conductivity and slow Zn2+ diffusion. Here, an electrochemically induced phase transformation strategy is proposed to mitigate and overcome these barriers. In situ X-ray diffraction analysis confirms the complete transformation of tunnel-like structural V6O13 into layered V5O12·6H2O during the initial electrochemical charging process. Theoretical calculations reveal that the phase transformation is crucial to reducing the Zn2+ migration energy barrier and facilitating fast charge storage kinetics. The calculated band structures indicate that the bandgap of V5O12·6H2O (0.0006 eV) is lower than that of V6O13 (0.5010 eV), which enhanced the excitation of charge carriers to the conduction band, favoring electron transfer in redox reactions. As a result, the transformed V5O12·6H2O delivers a high capacity of 609 mA h g-1 at 0.1 A g-1, superior rate performance (300 mA h g-1 at 20 A g-1), fast-charging capability (<7 min charging for 465 mA h g-1), and excellent cycling stability with a reversible capacity of 346 mA h g-1 at 5 A g-1 after 5000 cycles.

Oxygen Vacancies on NH4 V4 O10 Accelerate Ion and Charge Transfer in Aqueous Zinc-Ion Batteries.

Vanadium-based compounds are identified as promising cathode materials for aqueous zinc ion batteries due to their high specific capacity. However, the low intrinsic conductivity and sluggish Zn2+ diffusion kinetics seriously impede their further practical application. Here, oxygen vacancies on NH4 V4 O10 is reported as a high-performing cathode material for aqueous zinc ion batteries via a facile hydrothermal strategy. The introduction of oxygen vacancy accelerates the ion and charge transfer kinetics, reduces the diffusion barrier of zinc ions, and establishes a stable crystal structure during zinc ion (de-intercalation). As a result, the oxygen vacancy enriched NH4 V4 O10 exhibits a high specific capacity of ≈499 mA h g-1 at 0.2 A g-1 , an excellent rate capability of 296 mA h g-1 at 10 A g-1 and the specific capacity cycling stability with 95.1% retention at 5 A g-1 for 4000 cycles, superior to the NVO sample (186.4 mAh g-1 at 5 A g-1 , 66% capacity retention).

KCl Treatment of CdS Electron-Transporting Layer for Improved Performance of Sb2(S,Se)3 Solar Cells.

Antimony sulfoselenide (Sb2(S,Se)3) is a promising light absorption material because of its high photoabsorption coefficient, appropriate band gap, superior stability, and abundant elemental storage. As an emerging solar material, hydrothermal deposition of Sb2(S,Se)3 solar cells has enabled a 10% efficiency threshold, where cadmium sulfide (CdS) is applied as an electron transport layer (ETL). The high-efficiency Sb2(S,Se)3 solar cells largely employ CdS as the ETL. In terms of efficiency improvement, there are two questions regarding the CdS substrate: (1) the high roughness of CdS grown on F-doped tin oxide glass which increases the roughness of the absorber layer and (2) the low conductivity of CdS films because of low purity of CdS film grown by chemical bath deposition. In this study, we demonstrate an effective potassium chloride (KCl) post-treatment to modify the CdS ETL for improving the Sb2(S,Se)3 solar cell efficiency. We found that KCl plays dual roles that reduce roughness and enhance conductivity of the CdS films, thus acquiring a maximum efficiency of 9.98%, which is 9.2% higher than the control device. This study provides a new method for the surface engineering of CdS layer to improve the morphological and electrical properties, which is significant for improving the performance of CdS-based thin-film solar cells.

Cycling of block copolymer composites with lithium-conducting ceramic nanoparticles.

Solid polymer and perovskite-type ceramic electrolytes have both shown promise in advancing solid-state lithium metal batteries. Despite their favorable interfacial stability against lithium metal, polymer electrolytes face issues due to their low ionic conductivity and poor mechanical strength. Highly conductive and mechanically robust ceramics, on the other hand, cannot physically remain in contact with redox-active particles that expand and contract during charge-discharge cycles unless excessive pressures are used. To overcome the disadvantages of each material, polymer-ceramic composites can be formed; however, depletion interactions will always lead to aggregation of the ceramic particles if a homopolymer above its melting temperature is used. In this study, we incorporate Li0.33La0.56TiO3 (LLTO) nanoparticles into a block copolymer, polystyrene-b-poly (ethylene oxide) (SEO), to develop a polymer-composite electrolyte (SEO-LLTO). TEMs of the same nanoparticles in polyethylene oxide (PEO) show highly aggregated particles whereas a significant fraction of the nanoparticles are dispersed within the PEO-rich lamellae of the SEO-LLTO electrolyte. We use synchrotron hard x-ray microtomography to study the cell failure and interfacial stability of SEO-LLTO in cycled lithium-lithium symmetric cells. Three-dimensional tomograms reveal the formation of large globular lithium structures in the vicinity of the LLTO aggregates. Encasing the SEO-LLTO between layers of SEO to form a "sandwich" electrolyte, we prevent direct contact of LLTO with lithium metal, which allows for the passage of seven-fold higher current densities without signatures of lithium deposition around LLTO. We posit that eliminating particle clustering and direct contact of LLTO and lithium metal through dry processing techniques is crucial to enabling composite electrolytes.

Addition of Dioxane in Electrolyte Promotes (002)-Textured Zinc Growth and Suppressed Side Reactions in Zinc-Ion Batteries.

The reversibility and cyclability of aqueous zinc-ion batteries (ZIBs) are largely determined by the stabilization of the Zn anode. Therefore, a stable anode/electrolyte interface capable of inhibiting dendrites and side reactions is crucial for high-performing ZIBs. In this study, we investigated the adsorption of 1,4-dioxane (DX) to promote the exposure of Zn (002) facets and prevent dendrite growth. DX appears to reside at the interface and suppress the detrimental side reactions. ZIBs with the addition of DX demonstrated a long-term cycling stability of 1000 h in harsh conditions of 10 mA cm-2 with an ultrahigh cumulative plated capacity of 5 Ah cm-2 and shows a good reversibility with an average Coulombic efficiency of 99.7%. The Zn//NH4V4O10 full battery with DX achieves a high specific capacity (202 mAh g-1 at 5 A g-1) and capacity retention (90.6% after 5000 cycles), much better than that of ZIBs with the pristine ZnSO4 electrolyte. By selectively adjusting the Zn2+ deposition rate on the crystal facets with adsorbed molecules, this work provides a promising modulation strategy at the molecular level for high-performing Zn anodes and can potentially be applied to other metal anodes suffering from instability and irreversibility.

Analysis of the impact of noninvasive prenatal testing for trisomies 21 and 18 in twin pregnancies undergoing artificial reproductive technology.

PURPOSE: The purpose of this study was to evaluate the performance and impact of noninvasive prenatal screening (NIPS) on twin pregnancies. PATIENTS AND METHODS: Twin pregnancies after artificial reproductive technology(ART) were tested by NIPS for screening trisomy 21, 18, and 13 in a single medical center in Hangzhou. Positive NIPS results were confirmed by karyotyping, while negative results were interviewed after delivery. RESULTS: From January 2019 to December 2020, 474 twin pregnancies were tested by NIPS for screening trisomy 21, 18, and 13 in a single medical center in Hangzhou. The performance of NIPS had been evaluated compared to the invasive diagnostic results. The positive predictive value (PPV) of NIPS for chromosome 21 and 18 aneuploidies is 80% (95CI, 36.09-96.59) and 100%, respectively. The incidence of trisomy 21, and 18 chromosome aneuploidies among the twin pregnancies undergoing ART was 0.84% and 0.21%, respectively. CONCLUSION: The performance of NIPS was substantially accurate among the twin pregnancies after ART in this study, and NIPS potentially avoided a considerable part of aneuploidies liveborn in twin pregnancies in Hangzhou.

Regulating the Film Growth and Reducing the Defects for Efficient CsPbIBr2 Solar Cells.

Inorganic lead halide perovskite CsPbIBr2 possesses good stability with a suitable band gap for tandem solar cells. Decreasing the defect concentration and improving the film quality is crucial to further increase the power conversion efficiency of CsPbIBr2 solar cells. Here, the crystallization dynamics of CsPbIBr2 films is regulated by introducing the volatile organic salt, formamidinium acetate (FAAc) into the precursor solution. It is found that FAAc slows the crystallization process of CsPbIBr2 films and pinhole-free films with large grains and smooth surfaces are obtained. The defect concentration of the films is decreased and the nonradiative recombination is significantly inhibited. By improving the film quality, the FAAc remarkably enhances the efficiency of CsPbIBr2 solar cells. The champion device delivers a power conversion efficiency of 9.44% and exhibits higher stability than the reference device. This finding provides an effective strategy for reducing defects, suppressing the recombination, and improving the performance of CsPbIBr2 solar cells.

Synthesis of Antiperovskite Solid Electrolytes: Comparing Li3SI, Na3SI, and Ag3SI.

Prior calculations have predicted that chalcohalide antiperovskites may exhibit enhanced ionic mobility compared to oxyhalide antiperovskites as solid-state electrolytes. Here, the synthesis of Ag-, Li-, and Na-based chalcohalide antiperovskites is investigated using first-principles calculations and in situ synchrotron X-ray diffraction. These techniques demonstrate that the formation of Ag3SI is facilitated by the adoption of a common body centered cubic packing of S2- and I- in the reactants and products at elevated temperatures, with additional stabilization achieved by the formation of a solid solution of the anions. The absence of these two features appears to hinder the formation of the analogous Li and Na antiperovskites.

Toward Current Matching in Tandem Dye-Sensitized Solar Cells.

The tandem pn-type dye-sensitized solar cells (pn-DSCs) have received much attention in the field of photovoltaic technologies because of their great potential to overcome the Shockley-Queisser efficiency limitation that applies to single junction photovoltaic devices. However, factors governing the short-circuit current densities (Jsc) of pn-DSC remain unclear. It is typically believed that Jsc of the pn-DSC is limited to the highest one that the two independent photoelectrodes can achieve. In this paper, however, we found that the available Jsc of pn-DSC is always determined by the larger Jsc that the photoanode can achieve but not by the smaller one in the photocathode. Such experimental findings were verified by a simplified series circuit model, which shows that a breakdown will occur on the photocathode when the photocurrent goes considerably beyond its threshold voltage, thus leading to an abrupt increase in Jsc of the circuit. The simulation results also suggest that a higher photoconversion efficiency of the pn-DSCs can be only achieved when an almost equivalent photocurrent is achieved for the two photoelectrodes.

Probing Mg Intercalation in the Tetragonal Tungsten Bronze Framework V4Nb18O55.

While commercial Li-ion batteries offer the highest energy densities of current rechargeable battery technologies, their energy storage limit has almost been achieved. Therefore, there is considerable interest in Mg batteries, which could offer increased energy densities in comparison to Li-ion batteries if a high-voltage electrode material, such as a transition-metal oxide, can be developed. However, there are currently very few oxide materials which have demonstrated reversible and efficient Mg2+ insertion and extraction at high voltages; this is thought to be due to poor Mg2+ diffusion kinetics within the oxide structural framework. Herein, the authors provide conclusive evidence of electrochemical insertion of Mg2+ into the tetragonal tungsten bronze V4Nb18O55, with a maximum reversible electrochemical capacity of 75 mA h g-1, which corresponds to a magnesiated composition of Mg4V4Nb18O55. Experimental electrochemical magnesiation/demagnesiation revealed a large voltage hysteresis with charge/discharge (1.12 V vs Mg/Mg2+); when magnesiation is limited to a composition of Mg2V4Nb18O55, this hysteresis can be reduced to only 0.5 V. Hybrid-exchange density functional theory (DFT) calculations suggest that a limited number of Mg sites are accessible via low-energy diffusion pathways, but that larger kinetic barriers need to be overcome to access the entire structure. The reversible Mg2+ intercalation involved concurrent V and Nb redox activity and changes in crystal structure, as confirmed by an array of complementary methods, including powder X-ray diffraction, X-ray absorption spectroscopy, and energy-dispersive X-ray spectroscopy. Consequently, it can be concluded that the tetragonal tungsten bronzes show promise as intercalation electrode materials for Mg batteries.

Impacts of Oxygen Vacancies on Zinc Ion Intercalation in VO2.

The aqueous zinc ion battery has emerged as a promising alternative technology for large-scale energy storage due to its low cost, natural abundance, and high safety features. However, the sluggish kinetics stemming from the strong electrostatic interaction of divalent zinc ions in the host crystal structure is one of challenges for highly efficient energy storage. Oxygen vacancies (VO••), in the present work, lead to a larger tunnel structure along the b axis, which improves the reactive kinetics and enhances Zn-ion storage capability in VO2 (B) cathode. DFT calculations further support that VO•• in VO2 (B) result in a narrower bandgap and lower Zn ion diffusion energy barrier compared to those of pristine VO2 (B). VO••-rich VO2 (B) achieves a specific capacity of 375 mAh g-1 at a current density of 100 mA g-1 and long-term cyclic stability with retained specific capacity of 175 mAh g-1 at 5 A g-1 over 2000 cycles (85% capacity retention), higher than that of VO2 (B) nanobelts (280 mAh g-1 at 100 mA g-1 and 120 mAh g-1 at 5 A g-1, 65% capacity retention).

Two-dimensional triphenylene cored hole-transporting materials for efficient perovskite solar cells.

Two organic hole-transporting materials comprising a two-dimensional triphenylene core and methoxyl-arylamine terminal units are developed and applied in perovskite solar cells. Enhanced photovoltaic and stability performance are obtained using TPH-T compared with those of spiro-OMeTAD.

Hierarchical Porous Metallic V2O3@C for Advanced Aqueous Zinc-Ion Batteries.

Aqueous Zn-ion batteries (ZIBs) are a potential electrochemical energy storage device because of their highly intrinsic safety, low cost, and large capacity. However, it is still in the primary stage because of the limited selection of cathode materials with high rate and long-life cycling stability. In addition, the energy storage mechanisms of ZIBs have not been well established. In this work, we report the synthesis of porous V2O3@C materials with high conductivity and further illustrate its application as the intercalation cathode for aqueous zinc-ion batteries. The unique channel and appropriate pore size distribution of corundum-type V2O3 are beneficial to the rapid zinc ion intercalation and removal, leading to a high rate capability. Also, the carbon framework structure achieves a high cyclic stability. The porous V2O3@C cathode delivers high capacities of 350 mA h g-1 at 100 mA g-1, an excellent rate capability (250 mA h g-1 at 2 A g-1), and an impressive long-life cycling stability with 90% capacity retention over 4000 cycles at 5 A g-1. The storage mechanism of zinc ions in the Zn/V2O3 system was studied by various analytical methods and first-principles calculation.

Enhanced Interfacial Binding and Electron Extraction Using Boron-Doped TiO2 for Highly Efficient Hysteresis-Free Perovskite Solar Cells.

Perovskite solar cells (PSCs) have witnessed astonishing improvement in power conversion efficiency (PCE), more recently, with advances in long-term stability and scalable fabrication. However, the presence of an anomalous hysteresis behavior in the current density-voltage characteristic of these devices remains a key obstacle on the road to commercialization. Herein, sol-gel-processed mesoporous boron-doped TiO2 (B-TiO2) is demonstrated as an improved electron transport layer (ETL) for PSCs for the reduction of hysteresis. The incorporation of boron dopant in TiO2 ETL not only reduces the hysteresis behavior but also improves PCE of the perovskite device. The simultaneous improvements are mainly ascribed to the following two reasons. First, the substitution of under-coordinated titanium atom by boron species effectively passivates oxygen vacancy defects in the TiO2 ETL, leading to increased electron mobility and conductivity, thereby greatly facilitating electron transport. Second, the boron dopant upshifts the conduction band edge of TiO2, resulting in more efficient electron extraction with suppressed charge recombination. Consequently, a methylammonium lead iodide (MAPbI3) photovoltaic device based on B-TiO2 ETL achieves a higher efficiency of 20.51% than the 19.06% of the pure TiO2 ETL based device, and the hysteresis is reduced from 0.13% to 0.01% with the B-TiO2 based device showing negligible hysteresis behavior.

Tailoring the electrochemical activity of magnesium chromium oxide towards Mg batteries through control of size and crystal structure.

Chromium oxides with the spinel structure have been predicted to be promising high voltage cathode materials in magnesium batteries. Perennial challenges involving the mobility of Mg2+ and reaction kinetics can be circumvented by nano-sizing the materials in order to reduce diffusion distances, and by using elevated temperatures to overcome activation energy barriers. Herein, ordered 7 nm crystals of spinel-type MgCr2O4 were synthesized by a conventional batch hydrothermal method. In comparison, the relatively underexplored Continuous Hydrothermal Flow Synthesis (CHFS) method was used to make highly defective sub-5 nm MgCr2O4 crystals. When these materials were made into electrodes, they were shown to possess markedly different electrochemical behavior in a Mg2+ ionic liquid electrolyte, at moderate temperature (110 °C). The anodic activity of the ordered nanocrystals was attributed to surface reactions, most likely involving the electrolyte. In contrast, evidence was gathered regarding the reversible bulk deintercalation of Mg2+ from the nanocrystals made by CHFS. This work highlights the impact on electrochemical behavior of a precise control of size and crystal structure of MgCr2O4. It advances the understanding and design of new cathode materials for Mg-based batteries.

Mechanisms of Degradation and Strategies for the Stabilization of Cathode-Electrolyte Interfaces in Li-Ion Batteries.

Undesired reactions at the interface between a transition metal oxide cathode and a nonaqueous electrolyte bring about challenges to the performance of Li-ion batteries in the form of compromised durability. These challenges are especially severe in extreme conditions, such as above room temperature or at high potentials. The ongoing push to increase the energy density of Li-ion batteries to break through the existing barriers of application in electric vehicles creates a compelling need to address these inefficiencies. This goal requires a combination of deep knowledge of the mechanisms underpinning reactivity, and the ability to assemble multifunctional electrode systems where different components synergistically extend cycle life by imparting interfacial stability, while maintaining, or even increasing, capacity and potential of operation. The barriers toward energy storage at high density apply equally in Li-ion, the leading technology in the battery market, and in related, emerging concepts for high energy density, such as Na-ion and Mg-ion, because they also conceptually rely on electroactive transition metal oxides. Therefore, their relevance is broad and the quest for solutions inevitable. In this Account, we describe mechanisms of reaction that can degrade the interface between a Li-ion battery electrolyte and the cathode, based on an oxide with transition metals that can reach high formal oxidation states. The focus is placed on cathodes that deliver high capacity and operate at high potential because their development would enable Li-ion battery technologies with high capacity for energy storage. Electrode-electrolyte instabilities will be identified beyond the intrinsic potential windows of stability, by linking them to the electroactive transition metals present at the surface of the electrode. These instabilities result in irreversible transformations at these interfaces, with formation of insulating layers that impede transport or material loss due to corrosion. As a result, strategies that screen the reactive surface of the oxide, while reducing the transition metal content by introducing inactive ions emerge as a logical means toward interfacial stability. Yet they must be implemented in the form of thin passivating barriers to avoid unacceptable losses in storage capacity. This Account subsequently describes our current ability to build composite structures that include the active material and phases designed to address deleterious reactions. We will discuss emerging strategies that move beyond the application of such barriers on premade agglomerated powders of the material of interest. The need for these strategies will be rationalized by the goal to effectively passivate all interfaces while fully controlling the chemistry that results at the surface and its homogeneity. Such outcomes would successfully minimize interfacial losses, thereby leading to materials that exceed the charge storage and life capabilities possible today. Practically speaking, it would create opportunities to design batteries that break the existing barriers of energy density.

Solvothermal Synthesis of Hierarchical TiO2 Microstructures with High Crystallinity and Superior Light Scattering for High-Performance Dye-Sensitized Solar Cells.

In this article, hierarchical TiO2 microstructures (HM-TiO2) were synthesized by a simple solvothermal method adopting tetra-n-butyl titanate as the titanium source in a mixed solvent composed of N,N-dimethylformamide and acetic acid. Due to the high crystallinity and superior light-scattering ability, the resultant HM-TiO2 are advantageous as photoanodes for dye-sensitized solar cells. When assembled to the entire photovoltaic device with C101 dye as a sensitizer, the pure HM-TiO2-based solar cells showed an ultrahigh photovoltage up to 0.853 V. Finally, by employing the as-obtained HM-TiO2 as the scattering layer and optimizing the architecture of dye-sensitized solar cells, both higher photovoltage and incident photon-to-electron conversion efficiency value were harvested with respect to TiO2 nanoparticles-based dye-sensitized solar cells, resulting in a high power conversion efficiency of 9.79%. This work provides a promising strategy to develop photoanode materials with outstanding photoelectric conversion performance.

Enhancing the Photovoltaic Performance of Perovskite Solar Cells with a Down-Conversion Eu-Complex.

Organometal halide perovskite solar cells (PSCs) have shown high photovoltaic performance but poor utilization of ultraviolet (UV) irradiation. Lanthanide complexes have a wide absorption range in the UV region and they can down-convert the absorbed UV light into visible light, which provides a possibility for PSCs to utilize UV light for higher photocurrent, efficiency, and stability. In this study, we use a transparent luminescent down-converting layer (LDL) of Eu-4,7-diphenyl-1,10-phenanthroline (Eu-complex) to improve the light utilization efficiency of PSCs. Compared with the uncoated PSC, the PSC coated with Eu-complex LDL on the reverse of the fluorine-doped tin oxide glass displayed an enhancement of 11.8% in short-circuit current density (Jsc) and 15.3% in efficiency due to the Eu-complex LDL re-emitting UV light (300-380 nm) in the visible range. It is indicated that the Eu-complex LDL plays the role of enhancing the power conversion efficiency as well as reducing UV degradation for PSCs.

Nucleation and growth process of atomic layer deposition platinum nanoparticles on strontium titanate nanocuboids.

Uniform, well-dispersed platinum nanoparticles were grown on SrTiO3 nanocuboids via atomic layer deposition (ALD) using (methylcyclopentadienyl)trimethylplatinum (MeCpPt(Me)3) and water. For the first half-cycle of the deposition particles formed through two sequential processes: initial nucleation and growth. The final particle size after a single complete ALD cycle was dependent on the reaction temperature which alters the net Pt deposition per cycle. Additional cycles resulted in further growth of previously formed particles. However, the increase in size per cycle during additional ALD cycles, beyond the first, was significantly lower as less Pt was deposited due to carbonaceous material that partially covers the surface and prevents further MeCpPt(Me)3 adsorption and reaction. The increase in particle size was also temperature dependent due to changes in the net Pt deposition. Pt nanoparticles increased in size by 59% and 76% after 15 ALD cycles for reaction temperatures of 200 °C and 300 °C, respectively. There was minimal change in the number of particles per unit area as a function of reaction time, indicating that there was minimal Ostwald ripening or secondary nucleation for the reaction conditions.