Fei Xu

Lanthanide‐doped lead‐free perovskite nanocrystals are promising candidates for near‐infrared (NIR) optoelectronics, yet their performance is limited by inefficient exciton‐to‐lanthanide energy‐transfer, surface non‐radiative losses, and intrinsically slow 4f‐4f radiative transitions. Here, we report highly efficient Cs ₃ YCl ₆ :Sb ³⁺ , Nd ³⁺ nanocrystals enabling high‐performance NIR photoluminescence and electroluminescence. The isolated [YCl ₆ ] ³⁻ octahedral framework confines excitons and facilitates efficient Sb ³⁺ ‐induced localized defect‐state emission sensitization to Nd ³⁺ , leading to intense NIR emissions at 890, 1070, and 1350 nm with an ultra‐high NIR photoluminescence quantum yield (PLQY) of 65.9% for Nd ³⁺ ‐based lead‐free perovskite nanocrystals. Sotalol molecular passivation further suppresses surface non‐radiative recombination and improves energy‐transfer efficiency from 51.5% to 66.8%. Moreover, Cu _2‐x S is introduced as a semiconductor localized surface plasmon resonance layer, its broad NIR plasmonic absorption peak with a maximum near 1070 nm, overlaps well with the Nd ³⁺ emission, thereby selectively accelerating the spontaneous radiative decay at 890 and 1070 nm by 4.1‐and 9.2‐fold, respectively. Consequently, the optimized NIR light‐emitting diodes delivers a maximum external quantum efficiency (EQE) of 10.89%, a peak power density of 3.8 mW cm ⁻² , and a T ₅₀ lifetime of 389 min, representing a breakthrough among various rare earths‐doped NIR light‐emitting diodes.

The realization of efficient 1.54 µm electroluminescence from erbium ions is persistently hampered by their intrinsically small absorption cross-section and low excitation efficiency in conventional hosts. This study addresses this by synthesizing lead-free Cs₃CrBr₆ perovskite nanocrystals. This material is a direct-bandgap n-type chromium-based halide semiconductor whose electronic structure provides good charge transport, serving as a suitable host for lanthanide doping. Er³⁺ incorporation serves as an efficient luminescent center and modulates the host’s band structure. Leveraging the broadband absorption of Cr³⁺ for sensitization, combined with surface passivation, we achieve highly efficient Cr³⁺ to Er³⁺ energy transfer. This yields intense 1.54 µm emission with a photoluminescence quantum yield of 47%. The corresponding electroluminescent device attains a peak external quantum efficiency of 3.26%, among the highest values reported for solution-processed, Er³⁺-based near-infrared light-emitting diodes. This performance robustly validates the host’s effectiveness in facilitating charge injection and transport. Consequently, this work provides a viable material strategy for high-performance 1.54 µm emission and lays a solid foundation for chromium-based halide perovskites in advanced optoelectronics.

Ternary two-dimensional (2D) Nb2SiTe4 has recently garnered significant interest due to its exceptional stability under ambient conditions, a property rarely observed in conventional 2D semiconductors. Despite this advantage, the microscopic mechanism underpinning its environmental robustness remains unresolved. In typical 2D chalcogenides, instability is closely associated with electronically active surface anions, which facilitate the formation of anion vacancies and promote surface oxidation. In this work, we employ first-principles calculations to elucidate the electronic structure and intrinsic defect physics of Nb2SiTe4. Our results demonstrate that Te atoms in Nb2SiTe4 are electronically inert, contributing negligibly to the valence-band maximum as a consequence of weak Te-5p/Nb-4d hybridization. This inert electronic character gives rise to both the high formation energy and the delocalized defect state near the conduction band minimum of the Te vacancy. Removal of a Te atom enables direct Nb–Nb orbital interaction within the face-sharing trigonal prisms, generating an unoccupied bonding state that destabilizes the local coordination environment and renders the formation of Te vacancy energetically unfavorable. Moreover, pristine Nb2SiTe4 exhibits only weak adsorption of the O2 molecule, attributed to the limited electronic perturbation between Te and O2. Even in the presence of a Te vacancy, O2 adsorption induces minimal and highly localized charge transfer, indicating a strongly suppressed oxidation propensity relative to conventional 2D chalcogenides. Our findings reveal the intrinsic origin of the high anion-vacancy formation energy and outstanding oxidation resistance of Nb2SiTe4. This work provides fundamental insight into its exceptional environmental stability and underscores its suitability for reliable and durable 2D electronic applications.

Silver-bismuth iodide (ABI) ternary semiconductors, such as AgBi2I7, AgBiI4, Ag2BiI5, and Ag3BiI6, have emerged as promising lead-free light absorbers for photovoltaic applications due to their favorable optoelectronic properties. Despite recent advances that have improved power conversion efficiencies from ∼1% to over 5%, ABI-based solar cells still show substantial open-circuit voltage (VOC) losses of up to ∼1 V, which significantly hinder the device performance. These losses have been experimentally attributed to the non-radiative recombination originating from intrinsic defects, however, theoretical understanding of these defect mechanisms remains limited. Here, using density functional theory calculations, we systematically investigate the defect properties of AgBiI4. We identify the dominant intrinsic defects as acceptor-like Ag vacancies (VAg) and AgBi antisites, as well as donor-like Ag interstitials (Agi) and BiAg antisites. Among these defects, VAg and AgBi are shallow defects, while Agi and BiAg create deep trap states. Our calculations reveal that I-rich synthesis conditions with a carefully balanced Ag/Bi ratio are essential to suppressing the formation of deep defects and mitigating non-radiative recombinations. These insights provide theoretical guidance for defect modulation in ABI compounds and highlight AgBiI4 as a model system for understanding defect physics in ABI photovoltaic materials.

本文提出一种双吸收层钙钛矿异质结(Dual-absorption-layer Perovskite Heterojunction, DPHJ)策略，即通过将能带交错的II型钙钛矿异质结(p-pCsPbI₂Br-CsPbIBr₂)应用到全钙钛矿叠层太阳电池作为顶电池的双层结构的吸收层。电池模拟结果表明，与顶电池为单一吸收层CsPbI₂Br的全钙钛矿叠层太阳电池相比，DPHJ的引入使得叠层太阳电池的开路电压显著增强(从2.16 V到2.25 V)、短路电流密度进一步提升(从15.96 mA·cm^-2到16.76 mA·cm^-2)。这主要归因于顶电池的双层结构的吸收层在CsPbI₂Br/CsPbIBr₂界面处形成能带弯曲，诱导产生增强的内建电场，促进载流子输运，抑制了吸收层体内的非辐射复合。由此基于DPHJ策略的叠层太阳电池可达到高的理论能量转换效率(32.47%)。进一步实验结果表明，相比于单层CsPbI₂Br(激子结合能E₂=101.9 meV、电子-声子耦合强度(γ_ac=1.2×10^-2，γ_LO=6.9×10³)，双吸收层薄膜展现出更高的激子结合能(E₂=110.7 meV)和更低的电子-声子耦合强度(γ_ac=1.1×10^-2，γ_LO=6.3×10³)，表现出更强的光、热稳定性，这有利于制备长效稳定的全钙钛矿叠层太阳电池。

The realization of large‐area high‐quality perovskite thick films under an atmospheric environment without humidity control is confronting an urgent challenge for the applications in X‐ray detection and imaging. A spray‐coating method with air as the gas carrier is employed to achieve large‐area perovskite thick films for X‐ray flat‐panel detection applications. To further improve the quality of the thick films, the 10 µm‐thick CsPbIBr₂ films with (100)‐preferred orientation, low trap density (7.1 × 10¹² cm⁻³) and high resistivity corresponding to low dark current (3.2 × 10⁻⁹ A) are prepared via dual‐additive‐assisted (NH₄SCN and L‐α‐phosphatidylcholine (LP)) solution strategy under atmospheric environment with relative humidity of 60% (60% RH). Thus, the metal‐semiconductor‐metal‐structured (Au/CsPbIBr₂/Au) transverse X‐ray detection device under 40 KeV X‐ray irradiation possesses a high sensitivity up to 1420 µC Gy_air⁻¹ cm⁻² under a weak electric field of 18 V mm⁻¹ and a low dose rate of 3.3 µGy_air s⁻¹ that is lower than a dose rate of ≈5.5 µGy_air s⁻¹ required for routine medical diagnosis. Strikingly, the unencapsulated device maintains 80% (1120 µC Gy_air⁻¹ cm⁻²) of the original sensitivity after 1000 h under the atmospheric environment with 45–55% RH. These results pave the way for the practical applications of perovskite thick films in X‐ray medical detection and imaging.

It is fundamentally challenging to achieve stable and efficient all‐inorganic perovskite solar cells (PSCs) in ambient air conditions for low‐cost commercial manufacturing, as the crystallinity, surface morphology, and optical activity of all‐inorganic perovskites exhibit high sensitivity to environmental factors such as moisture and illumination. Herein, a dual‐doping strategy is presented to prepare high‐quality dual‐doping CsPbI₂Br films under ambient air with relative humidity of 70% (70% RH) by introducing CaCl₂ and InCl₃ additives into precursor solution. The results from the experiments and calculations reveal that the CaCl₂ additive can isolate moisture by forming hydrates at the surface and grain boundary of perovskites. Meanwhile, the addition of InCl₃ can significantly improve the optoelectronic properties via the heterovalent substitution of Pb²⁺ by a small amount of In³⁺. Moreover, the phase segregation can be significantly suppressed in the dual‐doping CsPbI₂Br films owing to decreasing the electron–phonon coupling strength and increasing the activation energy of ion migration. The unencapsulated dual‐doping CsPbI₂Br PSC with the power conversion efficiency (PCE) of 15.51% (70% RH) demonstrates high humidity storage and long‐term optical stability, remaining 90% of the original PCE after aging 2400 h under ambient air (50% RH) and 1500 h under continuous illumination, respectively.

本工作提出了一种对Cu₂ZnSnS₄中Zn元素异价取代策略，探讨了新型四元硫族化合物A₂M₂M'Q₄(A = Na、K、Rb、Cs、In、Tl；M = Cu、Ag、Au；M' = Ti、Zr、Hf、Ge、Sn；Q = S、Se、Te)作为新型太阳能电池吸收层材料的应用潜力。利用第一性原理高通量计算，评估了1350种A₂M₂M'Q₄化合物热力学稳定性、带隙、光谱极限最大效率和声子色散谱等特性。结果表明，有10种热力学和动力学稳定的候选材料，它们表现出合适的带隙和展现出高的光吸收性能，光谱极限最大效率的理论值均超过30%。它们的电子结构和光学性质类似于Cu₂ZnSnS₄，有望应用于高效单结薄膜太阳能电池。本文数据集可在https://www.doi.org/10.57760/sciencedb.j00213.00006 中访问获取 。( https://www.scidb.cn/s/naU7J3)