ACS Applied Energy Materials最新文献

We report on the optimization of in situ passivation of ink-based CuIn(S,Se)₂ thin-film solar cells via controlled incorporation of Al₂O₃ in CuIn(S,Se)₂ films by the addition of Al(NO₃)₃ to the molecular ink precursor. For this purpose, the Al/(Al + In) (AAI) metal ratio was varied from 0.05 to 0.30. We observe that the efficiency of the cells made of Al₂O₃-incorporated CuIn(S,Se)₂ is consistently higher than those without Al₂O₃, especially due to an improvement in open-circuit voltage (V_OC) and fill factor (FF), for all tested AAI ratios. With an AAI of 0.05, a maximum efficiency of 11.2% and an average efficiency of 8.5% (measured across 18 cells) was achieved, compared to 8.5% maximum efficiency and 6.5% average efficiency for Al-free CuIn(S,Se)₂. Furthermore, we find that cells made of Al₂O₃-incorporated CuIn(S,Se)₂ with an AAI of 0.2 show a narrow distribution in the photovoltaic performance, indicating higher reproducibility and higher FF. Energy-dispersive X-ray spectroscopy shows that, at AAI = 0.2, Al₂O₃ is distributed more homogeneously at the surface of the Al₂O₃-incorporated CISSe. Capacitance–voltage measurements reveal a reduced defect density by incorporation of Al₂O₃, which could be partly responsible for the higher V_OC. Furthermore, using detailed surface analysis with various X-ray and electron spectroscopy methods, we derive chemical and electronic structure information from the surface. With ultraviolet photoelectron (UPS) and inverse photoemission spectroscopies (IPES), the electronic band gap of the CuIn(S,Se)₂ thin-film surface is found to increase from 1.22 to 1.88 eV (±0.12 eV) with Al₂O₃ incorporation. This is accompanied by a clear reduction of the conduction band spike at the CdS/CISSe interface due to Al₂O₃ addition, as derived by both UPS and IPES as well as temperature-dependent V_OC measurements.

Subtle structural variations in covalent organic frameworks (COFs) can significantly alter their electronic structures and optoelectronic properties, thereby modulating their third-order nonlinear optical (NLO) performance. However, the systematic investigation of how imine bond orientation affects the third-order NLO properties of COFs remains unexplored. To address this, two pairs of imine bond orientational isomers (DA-COF1/DA-COF2 and DA-COF3/DA-COF4) were designed and synthesized. The experimental results demonstrate that DA-COF1 films exhibited saturation absorption (SA) at all pulse energies, while DA-COF2, DA-COF3, and DA-COF4 films exhibited optical switching characteristics and were inverse saturation absorption (RSA) at low energy, which was transformed into SA with increasing energy. At a pulse energy of 5 μJ, the nonlinear absorption coefficient |β| of DA-COF1 (23.4 × 10^–7 m/W) and DA-COF3 (10.2 × 10^–7 m/W) is 2.31 and 2.04 times that of DA-COF2 (10.1 × 10^–7 m/W) and DA-COF4 (5.0 × 10^–7 m/W), respectively. Besides, the third-order nonlinear polarizability χ⁽³⁾ of DA-COF1 (6.22 × 10^–7 esu) and DA-COF3 (5.06 × 10^–7 esu) is 1.31 and 1.66 times that of DA-COF2 (4.76 × 10^–7 esu) and DA-COF4 (3.05 × 10^–7 esu), respectively. These results further illustrate that compared with D-C═N-A configured COFs (DA-COF2 and DA-COF4), A-C═N-D configured COFs (DA-COF1 and DA-COF3) exhibit narrower bandgaps, lower fluorescence intensity, highly symmetrical electron cloud density, and stronger intramolecular charge transfer efficiency, consequently demonstrating superior third-order NLO performance. In summary, subtle differences in imine bond orientation significantly regulate third-order NLO performance, providing references for COFs’ applications in NLO and chemical bond orientation design.

While the melting method is promising for scalable production of Zintl-phase thermoelectrics, fabricating n-type Mg₃Sb₂ via this route remains challenging due to severe Mg volatilization. Building upon the concept of stepwise Mg compensation, this study introduces a key optimization: the symmetrical placement of Mg chips on both surfaces of the pellet during spark plasma sintering, as opposed to single-side compensation. This designed double-sided compensation strategy proves critical in achieving uniform and sufficient Mg supplementation throughout the bulk material. Combined with Bi doping at Sb sites to synergistically enhance phonon scattering and modify electronic transport, this approach yields exceptional thermoelectric performance. The optimized composition, Mg_3.9(Sb_0.75Bi_0.25)_1.99Te_0.01 with 14 wt % Mg compensation, achieves a peak ZT value of 1.19 at 723 K. Our work validates that the symmetrical stepwise compensation strategy is a robust and effective route for realizing high-performance n-type Mg₃Sb₂-based materials via the melting method.

Lithium sulfide (Li₂S) is an attractive high-capacity cathode material for lithium–sulfur batteries (LSBs) that enables lithium-anode-free designs with improved safety and simpler manufacturing. However, conventional fabrication methods often yield poor Li₂S confinement in mesoporous carbon host, restricting electrochemical performance. Here, we present a facile multicycle precursor infiltration-decomposition strategy to synthesize Li₂S@C nanocomposites with high in-pore Li₂S loading. Using mesoporous Super P (SP) as the conductive host and lithium trithiocarbonate (Li₂CS₃) as the precursor, sequential infiltration-decomposition cycles progressively increased the pore filling factor (FF) and in-pore Li₂S loading (IPL), from FF = 38% and IPL = 30% for Li₂S@SP-1 (one cycle) to FF = 91% and IPL = 73% for Li₂S@SP-5 (five cycles), while maintaining a total Li₂S loading of 70 wt %. Structural analyses of Li₂S@SP-5 by XRD and SEM confirmed reduced crystallite size, suppressed external deposition, and more uniform Li₂S distribution, contributing to significantly enhanced battery performance relative to Li₂S@SP-1. Compared to a sulfur-based S@SP counterpart, Li₂S@SP-5 showed superior performance due to the intrinsic volume contraction of Li₂S upon charging, which confined sulfur species within the pores and mitigated shuttle effects. Furthermore, full cells paired with Si/C anodes achieved high reversible capacities, demonstrating the viability of lithium-anode-free configurations. This work establishes multicycle infiltration-decomposition as a broadly applicable and scalable strategy to achieve high in-pore Li₂S loading, offering a promising pathway toward practical, high-energy-density Li₂S-based batteries.

Despite the promising sodium-storage characteristics of NASICON-type Na₃MnTi(PO₄)₃ arising from its stable three-dimensional framework and high ionic conductivity, its practical performance remains limited by the low Ti³⁺/Ti⁴⁺ redox potential, poor electronic conductivity, and Mn³⁺-induced Jahn–Teller distortion. In this study, Na₃MnTi_1–xNb_x(PO₄)₃ (x = 0, 0.025, 0.05, 0.075, 0.1) was synthesized via a sol–gel method. X-ray diffraction confirms that Nb⁵⁺ substitution at Ti sites preserves the NASICON structure while slightly expanding the lattice and promoting Na⁺ transport. Electrochemical tests show that appropriate Nb doping not only increases the high-voltage capacity corresponding to the Mn²⁺→ Mn⁴⁺ redox process, but also improves the rate capability, cycling stability, and reversibility of Na₃MnTi_1–xNb_x(PO₄)₃ cathodes. The Na₃Ti_0.95Nb_0.05Mn(PO₄)₃ sample delivered an initial capacity of 139.0 mAh g^–1 and maintained 74.1 mAh g^–1 after 500 cycles at 180 mA g^–1. Moreover, it exhibits enhanced rate capability, maintaining 88.6 mAh g^–1 as the current density increases to 900 mA g^–1. These findings indicate that Nb-doping is an effective strategy to enhance the electrochemical performance and structural stability of Na₃MnTi(PO₄)₃.

Combined experimental and simulation-based studies have been conducted to evaluate the role of electron transport layers (ETLs) in cesium lead bromide (CsPbBr₃) based perovskite solar cells. CsPbBr₃ thin films are fabricated through a multistep spin-coating method and are characterized using XRD, HR-SEM, UV–vis absorption, and infrared spectroscopy. The performance of TiO₂ and SnO₂ as ETLs is systematically unveiled for better layering to obtain higher efficiency. SnO₂-based device demonstrates a higher power conversion efficiency (PCE) of 4.97% (V_OC = 1.10 V, J_SC = 7.98 mA/cm², FF = 55.92%), outperforming the TiO₂-based device with a PCE of 3.86% (V_OC = 1.10 V, J_SC = 7.88 mA/cm², FF = 43.94%). Device-to-device uniformity is confirmed by the intrabatch variation of PCE for multiple runs, with a variation of ±2%, indicating excellent reproducibility of the devices. Numerical simulations are further employed to examine the influence of absorber thickness, bulk and interfacial defect densities, series resistance, and operational temperature on device performance. The simulation studies show that the SnO₂-based structure with Spiro-OMeTAD as the hole transport layer (HTL) achieves a maximum PCE of 8.08%. These experimental and theoretical insights confirm that SnO₂ functions as a superior ETL compared to TiO₂, thereby enabling the development of efficient and stable CsPbBr₃ perovskite solar cells under ambient conditions.

Molecular dynamics (MD) simulations were carried out to determine the impact of the cationic valence on the thermodynamic properties of the MOX (Mixed Oxide) samples. It has been found recently that U and Pu cations can coexist with various valences in near-stoichiometric and hypostoichiometric samples. Moreover, the CALPHAD method predicts a variation of valence concentrations with increasing temperature. As a consequence, this work investigates the effect of pentavalent and trivalent cations on the thermodynamic properties, i.e., lattice parameter, thermal expansion, and heat capacity. Stoichiometric conditions in MOX systems were studied by considering pentavalent and trivalent cation concentrations between 0 and 0.08. In addition, two charge compensation mechanisms arising under hypostoichiometric conditions─particularly those involving U⁵⁺ and Pu³⁺, together with the resulting variation in O/M─were examined. This work highlights for the first time the influence of these elements on MOX fuel properties, in particular, on the Bredig transition. The lattice parameters, linear thermal expansion coefficients, and heat capacities were calculated.

LiFePO₄ has been extensively employed as a cathode material for lithium-ion batteries due to its excellent thermal stability, safety, and long cycle life. However, its practical applications are still hindered by intrinsically low electronic conductivity and sluggish lithium-ion diffusion kinetics. Additionally, the precursor stoichiometry and thermal treatment conditions significantly influence the crystal structure and electrochemical performance. In this study, LiFePO₄ was systematically investigated by varying the Li/Fe molar ratios (1.03, 1.05, and 1.07) and sintering temperatures (730 °C, 750 °C, and 770 °C) to evaluate their effects on structural evolution, impurity phase formation, electrochemical properties, and Li⁺ transport behavior. The results demonstrate that a moderate lithium excess (Li/Fe = 1.03) combined with a lower sintering temperature (730 °C) effectively suppresses the formation of inert impurities such as Li₃PO₄, maintains high crystallinity, and optimizes the unit cell structure, thereby facilitating smoother Li⁺ migration pathways. Under these optimized conditions, the material exhibits the highest discharge capacity (162.62 mAh g^–1), minimal polarization, and superior rate performance. Electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration techniques (GITT) further confirm that the sample achieves the highest lithium-ion diffusion coefficient, reaching 1.27 × 10^–12 cm² s^–1. This study clearly demonstrates that tailoring the precursor stoichiometry and sintering parameters can synergistically enhance the structural stability, electrical conductivity, and Li⁺ transport kinetics of LiFePO₄, providing theoretical insights and practical guidance for the scalable production of high-performance LiFePO₄-based cathode materials

Developing efficient and sustainable electrocatalysts for the oxygen evolution reaction (OER) is essential for advancing renewable energy technologies, particularly in terms of achieving cost-effective and scalable solutions. In this work, two homoleptic cobalt(III) complexes (complex 1 and complex 2) were synthesized using a Schiff base derived from flexible salicylamine derivatives and bulky 3,5-ditert-butylsalicylaldehyde. This ligand-engineering strategy creates a favorable balance between electronic stability and conformational flexibility, facilitating the generation of catalytically active sites under operating conditions. Structural analysis by single-crystal X-ray diffraction revealed that both complexes crystallize as homoleptic species, [L^OMe₂Co]⁻ and [L^OEt₂Co]⁻, featuring a cobalt center in a distorted octahedral geometry with a +3 oxidation state, while triethylammonium ions act as counterions. Electrochemical studies demonstrated promising OER activity for both systems: complex 1 required an overpotential of 334 mV at 10 mA cm^–2 with a Tafel slope of 63 mV dec^–1, whereas complex 2 showed an overpotential of 348 mV with a Tafel slope of 70 mV dec^–1. These findings highlight the potential of cobalt-based molecular complexes as cost-effective, earth-abundant electrocatalysts for sustainable energy applications.

Fe-doped MnO₂ (Fe–MnO₂) was prepared to address the low conductivity of MnO₂ and applied as an electrocatalyst for lithium–oxygen batteries. MnO₂ was hydrothermally synthesized by using sacrificial single-walled carbon nanotubes (SWCNTs, consumed during the reaction) and subsequently blended with fresh SWCNTs to fabricate electrodes. Fe–MnO₂ was obtained by the same method with the addition of FeSO₄·7H₂O. Scanning and transmission electron microscopies, X-ray diffraction, and X-ray absorption fine structure (XAFS) confirmed the formation of uniformly distributed nanosheets with low crystallinity. Compared with the MnO₂/SWCNT electrode, the Fe–MnO₂/SWCNT electrode exhibited lower resistance, delivered higher discharge capacity, and maintained stable operation over 100 cycles. Time-resolved operando Mn K-edge XAFS revealed that Fe–MnO₂ sustains a higher average Mn valence (about +0.2 relative to undoped MnO₂) and suppresses the discharge-induced loss of the second-shell Fourier-transformed magnitude associated with the cleavage of edge-sharing MnO₆ octahedra, followed by substantial recovery upon charging. These findings indicate that Fe doping strengthens Mn–O bonding and mitigates Jahn–Teller-driven distortions, thereby enhancing durability. Long-term cycling tests nevertheless showed, through post-test XAFS measurements, that both Mn and Fe were reduced. The results were consistent with the possible formation of metallic nanoparticles with low coordination numbers after 311 cycles. Thus, while it was primarily introduced to improve conductivity, Fe doping was also found to enhance catalytic durability.