Key Takeaways & Executive Findings
- •• • Dark current density reduced to 3.1 μA/cm² at 0 V, a >3-fold improvement over unpassivated baseline, directly lowering power consumption and noise in eSWIR focal plane arrays. • • Specific detectivity of 8.79 × 10⁹ Jones at 2.5 μm and responsivity of 0.79 A/W, enabling room-temperature operation competitive with cooled InGaAs detectors. • • Response time of 19.6 μs and linear dynamic range >66 dB, supporting high-speed eSWIR imaging and spectroscopy without signal saturation. • • R₀A product of 8.78 Ω cm² at 300 K and 6.16 kΩ cm² at 80 K, demonstrating a 700-fold improvement upon cooling, which is critical for low-noise astronomical and defense applications.
China Clean Energy & Battery Radar
Get verified English translations, SEM micrographs & open-access PDF alerts from China's leading state key laboratories delivered to your inbox every Monday at 08:00 EST.
Abstract
Liquid-phase chemically deposited lead sulfide (PbS) thin films are a cost-effective platform for extended short-wavelength infrared (eSWIR) detection, yet their performance is constrained by high densities of sulfur vacancies and oxygen-in-sulfur defects formed during deposition. This work introduces chloride ions as an in-situ additive during chemical bath deposition to passivate these defects. The similar ionic radius of Cl⁻ (176 pm) to S²⁻ (179 pm) and its coordination with Pb²⁺ enable substitutional incorporation without significant lattice distortion. The passivated films exhibit a near-unity Pb/S atomic ratio, a photoluminescence full-width at half-maximum of 75 meV, and a carrier lifetime increase exceeding 20-fold. Homojunction photodiodes fabricated from these films demonstrate a dark current density of 3.1 μA/cm² at 0 V, a responsivity of 0.79 A/W at 2.5 μm, a specific detectivity of 8.79 × 10⁹ Jones, and a response time of 19.6 μs. The resistance-area product (R₀A) reaches 8.78 Ω cm² at 300 K and 6.16 kΩ cm² at 80 K. Activation energy analysis reveals trap-assisted tunneling as the dominant dark current mechanism at higher reverse biases, attributed to grain boundaries. These results represent among the best reported performance for PbS bulk thin-film photodiodes and offer a scalable route to high-performance eSWIR sensors.
1. Introduction
Extended short-wavelength infrared (eSWIR) detection (2–3 μm) is pivotal for eye-safe ranging, molecular spectroscopy, and low-visibility imaging. Commercial eSWIR photodiodes based on InGaAs or HgCdTe deliver high performance but require cryogenic cooling, complex epitaxial growth, and costly substrates, limiting their deployment in cost-sensitive and large-area applications. PbS, a narrow-bandgap semiconductor with a 300 K cutoff of 2.95 μm, offers a compelling alternative due to its intrinsic sensitivity across the full eSWIR band, low Auger recombination rate, and compatibility with solution-processed thin-film fabrication. However, liquid-phase chemical deposition of PbS polycrystalline films inevitably introduces sulfur vacancies and oxygen-in-sulfur defects, yielding carrier concentrations above 10¹⁷ cm⁻³ and high dark current densities that degrade detectivity and response speed.
Prior passivation strategies—such as post-deposition ligand exchange or halide treatment—often require additional processing steps, risk lattice damage, or fail to address bulk defects uniformly. This study pioneers the use of chloride ions as an in-situ additive during chemical bath deposition. The near-identical ionic radii of Cl⁻ (176 pm) and S²⁻ (179 pm) allow substitutional incorporation that neutralizes sulfur vacancies while coordinating with Pb²⁺ to suppress oxygen incorporation. The resulting films exhibit a Pb/S ratio near unity, a 20-fold increase in carrier lifetime, and a photoluminescence FWHM of 75 meV. The fabricated p-n homojunction photodiodes achieve a dark current density of 3.1 μA/cm², a responsivity of 0.79 A/W at 2.5 μm, and a specific detectivity of 8.79 × 10⁹ Jones, positioning them among the best PbS bulk thin-film photodiodes reported to date.
Loading authentic research manuscript (Pages 1–5)...
XU Shaoheng, LI Sen, ZHANG Wenyu, LUO Hao, LI Ruiming, LIN Qianqian, SONG Haisheng, LUO Jiajun, TANG Jiang (2025). Chloride-Passivated Lead Sulfide Thin Film for High-Performance Extended Short-Wavelength Infrared Photodiode. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3512-2
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the dominant dark current mechanism at high reverse bias, and how does it affect device reliability?
Activation energy analysis from 200–300 K shows Ea increasing from 0.109 eV at −10 mV to 0.172 eV at −0.5 V, which is below the half-bandgap of PbS (0.23 eV). This positive voltage dependence indicates trap-assisted tunneling current dominates at higher reverse biases, primarily due to grain boundaries in the polycrystalline film. This mechanism can lead to excess noise and limit the maximum operating bias, necessitating interface engineering or grain boundary passivation for high-voltage applications.
How does the chloride-passivated PbS photodiode compare to commercial InGaAs detectors in terms of cost and performance?
The PbS photodiode achieves a specific detectivity of 8.79 × 10⁹ Jones at 2.5 μm and a responsivity of 0.79 A/W at room temperature, with a dark current density of 3.1 μA/cm². While InGaAs detectors typically offer higher detectivity (∼10¹² Jones) and faster response, they require expensive epitaxial growth and often cooling. The PbS device, fabricated via low-cost chemical bath deposition, provides a viable path for cost-sensitive eSWIR applications where moderate performance suffices, with the added benefit of operation at elevated temperatures.
What are the scalability challenges for incorporating chloride ions into large-area PbS films?
The in-situ chloride addition is compatible with standard chemical bath deposition, which is inherently scalable for large-area and non-planar substrates. However, maintaining uniform chloride concentration across large batches requires precise control of bath chemistry, temperature, and deposition time. The study reports a Pb/S atomic ratio near unity and a 20-fold carrier lifetime improvement, but uniformity data on wafer-scale films are not provided. Future work must address reproducibility and waste management of chloride-containing baths.
What is the operational lifetime and stability of the chloride-passivated PbS photodiode under ambient conditions?
The paper does not report long-term stability tests. The device exhibits a dark current density of 3.1 μA/cm² at 0 V and a response time of 19.6 μs, but degradation rates under humidity, temperature cycling, or bias stress are unknown. Given the hygroscopic nature of PbS and potential chloride migration, encapsulation and accelerated aging tests are essential to qualify the technology for industrial deployment.
How does the R₀A product at 80 K (6.16 kΩ cm²) translate to detectivity limits for low-background applications?
The R₀A product of 6.16 kΩ cm² at 80 K is a 700-fold improvement over the 300 K value (8.78 Ω cm²), indicating a significant reduction in thermal noise. For a 1 mm² detector, this corresponds to a shot-noise-limited detectivity that could exceed 10¹² Jones at 80 K, assuming unity quantum efficiency. However, trap-assisted tunneling current, identified as the primary dark current component, may still limit performance at high reverse biases, necessitating further reduction of grain boundary defects for ultimate low-background performance.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.