Lithium Doping Research Articles

By using Doctor Blade Method, Lithium and Magnesium Co-Doped with Nickel Oxide Thin Film as Charge Transport Layer for Inorganic Perovskite Solar Cell

The organic materials for hole transport layer HTL such as PEDOT: PSS and Spiro-OMeTAD are poor electron blockers, more expensive, unstable, and large charge recombination materials. The inorganic material such as nickel oxide and copper oxide thin film for hole transport layer HTL was used to enhance the fill factor FF, power conversion efficiency PCE and stability of the hole transport layer for inorganic perovskite solar cell. Lithium and Magnesium co-doped with nickel oxide nanoparticles deposited on indium doped tin oxide ITO glass then deposited the cesium lead iodide bromide layer by using doctor blade method then characterize this thin film for confirmed the properties of the materials.
 The crystal structure of nickel oxide was measured from XRD and all the peaks were matched with JCPDS cards. The average crystalline size was 24 nm has cubic in shape. For optical properties and bandgap measured, using UV visible and DRS confirmed the strong absorbance near to the visible range, and bandgap decreased from 3.7 to 3.4 eV by adding doping. After the deposition of the inorganic perovskite layer, the bandgap decreased from 3.09 eV to 2.56 eV. RBS confirmed the chemical composition, impurity, and thickness of the thin film. The IV curve measurement showed the 4.3 % efficiency of the pure nickel oxide thin film, by adding the doping of lithium and magnesium in nickel oxide thin film showed the 7.65 % efficiency with the 83 % fill factor FF.

Future searches for light sterile neutrinos at nuclear reactors

We study the optimization of a green-field, two-baseline reactor experiment with respect to the sensitivity for electron antineutrino disappearance in search of a light sterile neutrino. We consider both commercial and research reactors and identify as key factors the distance of closest approach and detector energy resolution. We find that a total of 5 tons of detectors deployed at a commercial reactor with a closest approach of 25 m can probe the mixing angle $\sin^22\theta$ down to $\sim5\times10^{-3}$ around $\Delta m^2\sim 1$ eV$^2$. The same detector mass deployed at a research reactor can be sensitive up to $\Delta m^2\sim20-30$ eV$^2$ assuming a closest approach of 3 m and excellent energy resolution, such as that projected for the Taishan Antineutrino Observatory. We also find that lithium doping of the reactor could be effective in increasing the sensitivity for higher $\Delta m^2$ values.

Improved electrical properties of cuprous thiocyanate by lithium doping and its application in perovskite solar cells

Perovskite solar cells have attracted extensive attention because of their photoelectric characteristics. Since 2009, the photoelectric conversion rate of the solar cells has soared from 3.8% to 25.7% now. Perovskite materials have become the focus of extensive academic research due to their advantages of high carrier mobility, low exciton binding energy, wide absorption spectrum and high optical absorption coefficient However, organic P-type semiconductor materials are usually used as the hole transport layer in high efficiency perovskite solar cells. For example, Spiro-OMeTAD, PEDOT: PSS, PTAA, etc. Because Spiro-OMeTAD is difficult to be purified, many hole transport materials containing triphenylamine like Spiro-OMeTAD have been synthesized, such as triphenylamine polymer PTAA. As the conjugate parts of these triphenylamine transport materials are not coplanar and the space is distorted, they cannot form ordered stacks by spin-coating method, so their charge properties are weak, and li-TFSI and tBP are often added to improve the hole transport, so as to achieve better device effects. Moreover, PTAA has the problem of infiltration, and it is difficult to form a completely covered perovskite film on it, which seriously affects the quality and surface morphology of perovskite film. PEDOT: PSS itself has an acidic and corrosive electrode, and is easy to absorb moisture, which will affect the stability of the solar cell. The performance of organic materials will deteriorate seriously under environmental factors such as humidity, temperature and UV irradiation, which will accelerate the aging of perovskite solar cells and become one of the main obstacles to their practical application. In this work, inorganic cuprous thiocyanate (CuSCN) was used as a hole transport material, CuSCN is a rich and stable P-type semiconductor material, which has the characteristics of abundant, low cost, high carrier mobility, appropriate energy level, low defect density, good thermal stability and excellent light transmittance. CuSCN is one of the few known compounds with both high optical transparency (its wide band gap is 3.7-3.9 eV) and significant P-type electrical conductivity. Most importantly, CuSCN is inexpensive and can be prepared by solution method at room temperature. And its hole transport properties were improved by lithium doping. On this basis, the surface of CuSCN was modified with PTAA to avoid the interaction between CuSCN and lead iodide (PbI<sub>2</sub>), and the preparation of large-grained and dense perovskite films was realized. Finally, the performance of perovskite solar cells was effectively improved. This work provides a reference strategy for the preparation of stable and efficient perovskite solar cells.

Improved electrical properties of cuprous thiocyanate by lithium doping and its application in perovskite solar cells

Perovskite solar cells have attracted extensive attention because of their photoelectric characteristics. Since 2009, the photoelectric conversion rate of the solar cells has soared from 3.8% to 25.7%. Perovskite material has become a focus of extensive academic research due to its advantages of high carrier mobility, low exciton binding energy, wide absorption spectrum and high optical absorption coefficient. However, organic P-type semiconductor material is usually used as a hole transport layer in high efficiency perovskite solar cells, for example, Spiro-OMeTAD, PEDOT:PSS, and PTAA. Because Spiro-OMeTAD is difficult to purify, many hole transport materials containing triphenylamine like Spiro-OMeTAD have been synthesized, such as triphenylamine polymer PTAA. As the conjugate parts of these triphenylamine transport materials are not coplanar and the space is distorted, they cannot form ordered stacks by spin-coating method, so their charge properties are weak, and li-TFSI and tBP are often added to improve the hole transport, so as to achieve better device effects. Moreover, the PTAA has the problem of infiltration, and it is difficult to form a completely covered perovskite film on it, which seriously affects the quality and surface morphology of perovskite film. The PEDOT:PSS itself has an acidic and corrosive electrode, and is easy to absorb moisture, which will affect the stability of the solar cell. The performance of organic material will deteriorate seriously under environmental factors such as humidity, temperature and UV irradiation, which will accelerate the aging of perovskite solar cells and become one of the main obstacles to their practical applications. In this work, the inorganic cuprous thiocyanate (CuSCN) is used as a hole transport material, the CuSCN is a rich and stable P-type semiconductor material, which has the characteristics of abundance, low cost, high carrier mobility, appropriate energy level, low defect density, good thermal stability, and excellent light transmittance. The CuSCN is one of the few known compounds with both high optical transparency (its wide band gap is 3.7–3.9 eV) and significant P-type electrical conductivity. Most importantly, CuSCN is inexpensive and can be prepared by solution method at room temperature. And its hole transport properties are improved by lithium doping. On this basis, the surface of CuSCN is modified with PTAA to avoid the interaction between CuSCN and lead iodide (PbI<sub>2</sub>), and the large-grained and dense perovskite films are prepared. Finally, the performance of perovskite solar cells is effectively improved. This work provides a reference for the preparation of the stable and efficient perovskite solar cells.

New insights into NO adsorption on alkali metal and transition metal doped graphene nanoribbon surface: A DFT approach

The aim of this article is to investigate the sensing performance of NO gas molecule on the graphene nanoribbon domain for the determination of structural and electronic properties. Effect of an alkali metal (lithium) and a transition metal (iron) on the armchair oriented graphene nanoribbon (ArGNR) surface for the sensing purpose of NO gas has been performed through the quantum mechanics based Density Functional Theory (DFT) calculations. Various configurations of ArGNR doped with Li and Fe atoms such as one-edge doped, center doped, both-edge doped Li-ArGNR and Fe-ArGNR have been simulated, and a detailed comparative study of lithium and iron doping on different configurations of ArGNRs for the adsorption energy, stability analysis, band gap analysis and density of states analysis has been quantitatively evaluated. By comparing the adsorption energy of NO, it is found that Li doping enhances the strength of NO adsorption on the different variants of ArGNR. Computational results predict that the undoped ArGNR is insensitive to the NO gas adsorption with adsorption energy of about −0.41 eV. Our results determine that substitutional doping of Li doping at one edge doped and both-edge doped position increases the adsorption abilities of ArGNRs in these configurations with adsorption energies of approximately −6.92 eV and −9.64 eV that is 16 and 23 times greater than the pristine ArGNR (Pr-ArGNR). Band nature for both type of doping estimates the changing behavior of ArGNRs from semiconductor to metallic transition after the adsorption of NO molecule. It is concluded that the Li doping at one edge and both edge position of ArGNR makes it an excellent potential sensing material for the sensing purpose of NO gas as compared to the Fe doped configurations.

(Invited) Role of Lithium Doping in Layered Transition Metal Oxide Electrodes for Sodium Ion Batteries

Large-scale energy storage systems are urgently needed to enable the success of renewable but intermittent energy sources such as solar and wind power. Sodium ion batteries are a promising technology to address the need for large-scale energy storage systems, but their performance needs improvement to be competitive for this application. Dopants, especially lithium, have been shown to improve the performance of layered sodium transition metal oxide positive electrodes significantly. This talk will discuss the nature in which lithium is incorporated into the layered structures has a distinct effect on the modification of the electrodes’ properties, enhancing capacity and/or stability. A thorough understanding of the effect of lithium dopant location can inform the design of superior sodium ion battery positive electrode materials. High-temperature processing to tailor the positive electrode structures will also be discussed. High performance cathodes with lithium dopants may help address the growing challenge of large-scale energy storage to support renewable energy technology.

Role of Lithium Doping in P2-Na0.67Ni0.33Mn0.67O2 for Sodium Ion Batteries

P2-structured Na0.67Ni0.33Mn0.67O2 (PNNMO) is a promising Na-ion battery cathode material, but its capacity fading during cycling remains a hurdle. Li doping in layered transition-metal oxide (TMO) cathode materials is known to enhance their electrochemical properties. Nevertheless, the influence of Li at different locations in the structure has not been investigated. Here, the crystallographic role and electrochemical impact of lithium on different sites in PNNMO is investigated in Li x Na0.67–y Ni0.33Mn0.67O2+δ (0.00 ≤ x ≤ 0.2, y = 0, 0.1). Lithium occupancy on the Na layer is promoted in Na-deficient (Na < 0.67) PNNMO, evidenced by ex situ and operando synchrotron X-ray diffraction, X-ray absorption spectroscopy, and 7Li solid-state nuclear magnetic resonance. Partial substitution of Na with Li enhances cycling stability and specific capacity compared to PNNMO. In contrast, when lithium is located primarily on octahedral TM sites, capacity is increased but at the cost of stability.

(Invited) Operando X-Ray Absorption Fine Structure Studies of Polymer Electrolyte Membrane Electrolysis and Alkaline Water Electrolysis

With increasing global environmental problems, hydrogen, produced by renewable energies, has been considered a sustainable and clean fuel for next-generation energy sources[. Among the many proposed methods to produce hydrogen, the most renewable method is water electrolysis. However, the four electrons/protons needed for the oxygen evolution reaction (OER) in water electrolysis result in sluggish kinetics and low efficiency, representing the biggest obstacle for widespread applications. Polymer electrolysis membrane (PEM) electrolysis is expected to be commercialized due to its high current density, compact system, and high gas purity. Nevertheless, catalyst corrosion in acidic environments and high maintenance costs limit their general application. In contrast, alkaline water electrolysis (AWE) has been considered an alternative method for hydrogen production because earth-abundant transition-metal oxides (TM = Fe, Co, and Ni) can be used as catalysts, and certain states of TM cations accelerate the OER. Clarification of the electronic and local structure of catalysts during water electrolysis is important for understanding the activity and durability of catalysts. We have developed an operando X-ray Absorption Fine Structure (XAS) method that can be used to measure at high current densities under actual water electrolysis conditions. In this presentation, we will present examples of catalyst development using the established operando XAS method.Previous studies have focused on Ni-based oxides, including Ni(OH)2 and doped NiOOH, due to their low material cost, easily mediated structure, and high OER activity originating from various dopants, making them promising catalysts to replace noble metal oxides. Compared to Co-containing perovskite-type oxides, relatively few studies correlating the electronic states of Ni-based oxides with their OER activities have been reported. Recent studies on nickel oxides have elaborated the doping effect of lithium on catalyst activity, such as in LiNiO2 where lithium doping changed the local electronic structure of nickel, improving OER activity. LiNiO2 has a nominal oxidation state of Ni3+ and exhibits excellent OER activity considering the eg state descriptor. Moreover, because the energy levels of the Ni 3d orbitals of LiNiO2 are close to those of the O 2p orbitals, they can strongly hybridize. Therefore, LiNiO2 offers a suitable model to study the relationship between electronic structure and OER activity. However, for practical catalysts, the durability is also important and the deterioration mechanism of the LiNiO2 catalyst has not yet been clarified. LiNiO2, having an ordered rock salt structure, is a well-known cathode material for lithium-ion batteries, and exhibits extremely high lithium-ion mobility. Thus, catalyst degradation may be caused by de-intercalation of lithium ions during anodic polarization. In the Li-ion battery field, many studies have shown that the electrochemical properties of LiNiO2 cathodes are extremely dependent on the degree of cation mixing, primarily due to the presence of Ni2+ at Li+ and Ni3+ sites because of the similarity in their ionic radii. Cation mixing is a disadvantage for cathode materials because the presence of Ni2+ at Li+ sites hinders Li+ diffusion. Inspired by this, hindrance of the lithium diffusion path by cation mixing of Li and Ni is expected to be an effective solution when LiNiO2 is applied as an OER catalyst to improve stability. Herein, the cation mixing effect on OER activity and stability was studied using LixNi2-xO2. A combination of transmission electron microscopy (TEM), X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) investigations were conducted to probe the electronic structure of the materials. The valence changes of Ni during OER were further examined using operando XAS using a home-made flow-type cell. The degradation process was also investigated in detail using operando XAS.

Facile solution combustion synthesized, Li doped ZnO nanostructures for removal of abiotic contaminants

ZnO is a versatile photocatalytic material, yet it needed further modifications to explore it on the commercial scale. In the present study, photoactive Li doped ZnO nano-materials with different Li content were synthesized by adopting a facile low-temperature solution combustion approach. Li was introduced to improve ZnO characteristics correspond to photocatalytic efficiency. The effect of lithium doping on morphology, crystallinity, chemical state, and optical properties were investigated by utilizing various advanced techniques. The characterization analysis confirms the presence of thermally stable, well-crystalline wurtzite ZnO with a low bandgap and porous nature. Organic dye, Cibacron Red (CR), and a pesticide, Triclopyr (TC) were taken as model pollutants to evaluate the photodegradation performance of all samples under UV light source. Li doped ZnO nanomaterials containing 5 mol% Li attained the highest photocatalytic activity for the removal of both pollutants. The results of the study demonstrate that a strong electronic interaction between Li and ZnO results in the improvement of charge transferability and retards their recombination. The alteration in optical and surface properties of ZnO due to the substitution of Li into ZnO lattice was another reason for the superior activity of Li doped ZnO.

Role of Lithium Doping in P2-Na0.67Ni0.33Mn0.67O2 for Sodium-Ion Batteries.

P2-structured Na0.67Ni0.33Mn0.67O2 (PNNMO) is a promising Na-ion battery cathode material, but its rapid capacity decay during cycling remains a hurdle. Li doping in layered transition-metal oxide (TMO) cathode materials is known to enhance their electrochemical properties. Nevertheless, the influence of Li at different locations in the structure has not been investigated. Here, the crystallographic role and electrochemical impact of lithium on different sites in PNNMO is investigated in LixNa0.67–yNi0.33Mn0.67O2+δ (0.00 ≤ x ≤ 0.2, y = 0, 0.1). Lithium occupancy on prismatic Na sites is promoted in Na-deficient (Na < 0.67) PNNMO, evidenced by ex situ and operando synchrotron X-ray diffraction, X-ray absorption spectroscopy, and 7Li solid-state nuclear magnetic resonance. Partial substitution of Na with Li leads to enhanced stability and slightly increased specific capacity compared to PNNMO. In contrast, when lithium is located primarily on octahedral TM sites, capacity is increased but at the cost of stability.

Preparation of Li-Doped Indium-Zinc Oxide Thin-Film Transistor at Relatively Low Temperature Using Inkjet Printing Technology

Inkjet printing is a very attractive technology for printed electronics and a potential alternative to current high cost and multi-chemical lithography processes, for display and other applications in the electronics field. Inkjet technology can be employed to fabricate organic light emitting diodes (OLED), quantum dots displays, and thin-film transistors (TFTs). Among potential applications, metal oxide TFTs, which have good properties and moderate processing methods, could be prepared using inkjet printing in the display industry. One effective method of improving their electrical properties is via doping. Lithium doping an oxide TFT is a very delicate process, and difficult to get good results. In this study, lithium was added to indium-zinc oxide (IZO) for inkjet printing to make oxide TFTs. Electrical properties, transfer and output curves, were achieved using inkjet printing even at the relatively low annealing temperature of 200 oC. After optimizing the inkjet process parameters, a 0.01 M Li-doped IZO TFT at 400 oC showed a mobility of 9.08 ± 0.7 cm2/V s, a sub-threshold slope of 0.62 V/dec, a threshold voltage of 2.66 V, and an on-to-off current ratio of 2.83 × 108. Improved bias stability and hysteresis behavior of the inkjet-printed IZO TFT were also achieved by lithium doping.

Perovskite Quantum Dots as Multifunctional Interlayers in Perovskite Solar Cells with Dopant-Free Organic Hole Transporting Layers.

Perovskite solar cells (PSCs) with organic hole transporting layers (o-HTLs) have been widely studied due to their convenient solution processing, but it remains a big challenge to improve the hole mobilities of commercially available organic hole transporting materials without ion doping while maintaining the stability of PSCs. In this work, we demonstrated that the introduction of perovskite quantum dots (QDs) as interlayers between perovskite layers and dopant-free o-HTLs (P3HT, PTAA, Spiro-OMeTAD) resulted in a significantly enhanced performance of PSCs. The universal role of QDs in improving the efficiency and stability of PSCs was validated, exceeding that of lithium doping. After a deep examination of the mechanism, QD interlayers provided the multifunctional roles as follows: (1) passivating the perovskite surface to reduce the overall amount of trap states; (2) promoting hole extraction from perovskite to dopant-free o-HTLs by forming cascade energy levels; (3) improving hole mobilities of dopant-free o-HTLs by regulating their polymer/molecule orientation. What is more, the thermal/moisture/light stabilities of dopant-free o-HTLs-based PSCs were greatly improved with QD interlayers. Finally, we demonstrated the reliability of the QD interlayers by fabricating large-area solar modules with dopant-free o-HTLs, showing great potential in commercial usage.

On interface recombination, series resistance, and absorber diffusion length in BiI3 solar cells

Bismuth triiodide is a lead-free direct wide-bandgap solution-processable semiconductor that could be an alternative to lead-based perovskites in tandem or multijunction solar cells. However, the power conversion efficiency of single-junction BiI3 solar cells remains low. Here, we determine the main loss mechanisms of BiI3 solar cells in both n-i-p and p-i-n architectures. Overall, p-i-n devices have higher power conversion efficiency than that of n-i-p. It is found that n-i-p devices have higher (and significant) non-radiative recombination at the interface of the BiI3/transport layer, resulting in a lower open-circuit voltage than p-i-n devices. Moreover, the high series resistance (&amp;gt;70 Ω cm2) and a low average electron–hole diffusion length (∼60 nm) contributes to the low short-circuit current density (&amp;lt;5 mA/cm2) and fill factor (&amp;lt;40%) in all devices. In addition, interface recombination also reduces short-circuit current density. Finally, we demonstrate that lithium doping of BiI3 can increase the diffusion length of BiI3 to improve the performance of BiI3 solar cells. Solar cells with the configuration ITO/NiOx/Li:BiI3/PC61BM/bis-C60/LiF/Ag obtain a power conversion efficiency of 1.3% under AM 1.5 G illumination. The deep understanding of the main loss mechanisms of this work paves the way for future optimization of BiI3 solar cells.

Detailed crystallographic analysis of the ice V to ice XIII hydrogen-ordering phase transition

Ice V is a structurally highly complex material with 28 water molecules in its monoclinic unit cell. It is classified as a hydrogen-disordered phase of ice. Yet, some of its hydrogen-bonded water molecules display significant orientational order. Upon cooling pure ice V, additional orientational ordering cannot be achieved on the experimental time scale. Doping with hydrochloric acid has been shown to be most effective in enabling the phase transition of ice V to its hydrogen-ordered counterpart ice XIII. Here, we present a detailed crystallographic study of this phase transition investigating the effects of hydrochloric and hydrofluoric acid as well as lithium and potassium hydroxide doping. The magnitudes of the stepwise changes in the lattice constants during the phase transition are found to be more sensitive indicators for the extent of hydrogen order in ice XIII than the appearance of new Bragg peaks. Hydrofluoric acid and lithium hydroxide doping enable similar ordering processes as hydrochloric acid but with slower kinetics. The various possible space groups and ordered configurations of ice XIII are examined systematically, and the previously determined P21/a structure is confirmed. Interestingly, the partial hydrogen order already present in ice V is found to perpetuate into ice XIII, and these ordering processes are found to be independent of pressure. Overall, the hydrogen ordering goes along with a small increase in volume, which appears to be the origin of the slower hydrogen-ordering kinetics under pressure. Heating pressure-quenched samples at ambient pressure revealed low-temperature "transient ordering" features in both diffraction and calorimetry.

Grand canonical Monte Carlo simulations of methane adsorption in fullerene pillared graphene nanocomposites

The objective of this study is to investigate the methane adsorption performance of fullerene pillared graphene nanocomposites (FPGNs) with adjustable micro and meso porous morphology and high surface/weight ratios. Different types of fullerenes are considered as pillar units to adjust the porosity of FPGNs. The gravimetric, volumetric and deliverable methane storage capacities of FPGNs are examined using grand canonical Monte Carlo (GCMC) simulations. The lithium doping strategy is also employed to further improve the methane adsorption performance of FPGNs. GCMC simulations revealed that FPGNs have promising potential for methane storage applications with the appropriate selection of design parameters. In particular, the simulation results demonstrated that the gravimetric absolute methane uptake of FPGNs could reach 12.5 mmol/g at 298 K and 40 bars and, this value could be increased up to 19.7 mmol/g with appropriate doping ratio under the same conditions.

Lithium doping in spray-pyrolyzed NiO thin films: results on their microstructural, optical and electrochromic properties

The Li-doped NiO thin films were prepared onto the plane glass substrates, and the FTO coated glass substrates for electrochromic characterizations, employing the spray-pyrolysis technique. These films were analyzed by a variety of characterization techniques. The structural characterizations reveal that the as-prepared films are of NiO with a cubic structure along with the (2 2 0) plane as the most preferred orientation of crystallite growth. The topographic characterizations show that the surface roughness changes with the varying lithium content. The bandgap energy values are found in the range of 3.40–3.65 eV. Two emission peaks, one corresponding to NBE and another related to the structural defects, are observed in the room-temperature PL spectra of the films. The coloration efficiency of the films improves upon Li doping and is optimum (34.84 cm2/C at 550 nm) for the 3 at.% Li-doped films. The CA analyses indicate that the coloration phenomenon in the films occurs faster in comparison with the bleaching process. The EIS data have been examined based on an equivalent electrical circuit model using fit and simulation analysis.

High performance n-type thermoelectric material based on naphthalenediimide radical anions

An ideal organic thermoelectric (TE) material should possess features that would be low-cost, of high performance, easy to process, and non-toxic, but it is rare to find materials that meet these requirements. Naphthalenediimide (NDI), as a common and cheap industrial pigment, displays strong intermolecular inaction and good n-type semiconductor character. However, due to the strong interaction of π-π and hydrogen bond interaction, NDI usually exhibited poor solubility, making it difficult to process in solution. Herein, we demonstrated that the unsubstituted NDI could form a suspension mixed with NDI radical anion state by phenyl lithium doping, which consequently can be used to prepare dense film by drop-casting for TE application. More importantly, by optimizing the doping ratio, the TE film reached electrical conductivity of 0.11 S cm−1 and Seebeck coefficient of −1289 μV K−1. Eventually, a high power factor up to 18.8 μW m−1 K−2 and ZT value of 0.053 was obtained, which is one of the best TE performance achieved in n-type NDI-based TE materials. This work suggests the simple strategy of utilizing commercially mature molecules to develop organic TE materials with high performance.

Enhanced electrical properties of Li-salts doped mesoporous TiO2 in perovskite solar cells

<h2>Summary</h2> The charge transferability of the electron transfer layers (ETLs) is important for achieving high performance in mesoscopic (mp) perovskite solar cells (PSCs). However, because of the low electron extraction efficiency of TiO₂, lithium doping is essentially required. In this work, we compared the electrical properties of mp-TiO₂ doped with Li-salts with different anions—LiTFSI, Li₂CO₃, LiCl, and LiF. Interestingly, we found that the anions of the Li-salt dopants affect the electrical properties of the ETLs and the solar cell performance. The Li₂CO₃ doping of mp-TiO₂ led to conduction bands deeper than those of pristine mp-TiO₂ or other doped mp-TiO₂. The maximum efficiency of 25.28% and certified efficiency of 24.68% (Newport) was obtained by using Li₂CO₃ dopant. This optimization of the ETLs properties is expected to greatly contribute to the progress of PSCs by leading to further increases in their efficiency.

A P2/P3 composite-layered cathode material with low-voltage decay for sodium-ion batteries

Average discharge voltage of the P-type-layered oxides cathode materials is one of the key factors that determine the sodium-ion batteries (SIBs) performance, especially for the high energy density performance. Inspired by the strategy of lithium and magnesium doping in the transition metal layer to promote the anionic oxygen redox and the synergistic effect of composite materials for SIBs, we develop a layered P2/P3-Na0.75Li0.2Mg0.05Al0.05Mn0.7O2 composite cathode material enabled by the anionic oxygen redox. The synthesized composite delivers a reversible capacity of 180 mAh g−1 between 2.0 and 4.5 V at 0.2 C and keep ≈ 3.1 V stable average voltage above 2.5 V the discharge cutoff voltage. With a combination of the electrochemical performance, hard and soft X-ray absorption spectroscopy, we demonstrate that the irreversible anionic oxygen activity in the high-voltage region results in the capacity fading and the irreversible cationic manganese activity in the low-voltage region is responsible for the voltage decay. These findings provide a simple and effective method for designing low-voltage decay and high-energy density Na-deficient layered oxide composite.

Effect of commensurate lithium doping on the scintillation of two-dimensional perovskite crystals

Commensurate Lithium doping of two-dimensional lead halide perovskites leads to improved scintillation properties, with enhanced light yield, narrower energy resolution, higher radiation hardness and faster scintillation decay.