Nan Tian

HfO ₂ -based nonvolatile memristors have attracted broad research interest in neuromorphic computing. However, the stochastic nature of conductive filament formation poses significant challenges, including high operating voltages, low on/off ratios, limited endurance, and high device variability, which severely limits their applications in high-precision neuromorphic computing. To overcome these limitations and explore the potential of embedded metal nano‐island (NIs) arrays for performance enhancement, this study fabricated Pt/TaO _x /HfO ₂ /TiN, Pt/Ti/Al ₂ O ₃ /HfO ₂ /TiN devices, and a Ta NIs‐embedded device with the structure Pt/Ti/Al ₂ O ₃ /HfO ₂ /Ta NI/TiN, and investigated their corresponding resistive switching characteristics. The experimental results demonstrate that during multi‐level conductance state cycling tests, the Pt/TaO _x /HfO ₂ /TiN structure-benefiting from TaO _x as a thermal enhancement layer-exhibits a relatively low coefficient of variation (CV), with its conductance states showing completely non‐overlapping distributions. Notably, compared to the Pt/Ti/Al ₂ O ₃ /HfO ₂ /TiN structure, the Pt/Ti/Al ₂ O ₃ /HfO ₂ /Ta NI/TiN device with embedded Ta NIs achieves three core improvements: a notable decrease in operating voltages, greatly improved cycling consistency with significantly reduced CV of multi-level conductance, and effectively suppressed resistance drift in retention tests. Furthermore, the device shows excellent conductance state distinguishability in analog computing: its 8 independent conductance states remain fully separable under multiple pulse stimulation, with no overlap between adjacent states. These characteristics of HfO ₂ -based nonvolatile memristors can provide supportive assurance for the overall accuracy of neuromorphic computing systems.

This paper reports two copper-based organic-inorganic hybrid perovskite single crystals, (2A5MP)₂CuX₄ (X = Cl, Br), synthesized by a halogen-regulated method. Through comprehensive characterization (single-crystal XRD, powder XRD, FTIR, Raman spectroscopy, TGA, and UV-vis DRS), we elucidated crystal structures, intermolecular forces, functional groups, bond configurations, optical properties, and thermal stability. Both compounds crystallized in the monoclinic space group C2/c. (2A5MP)₂CuCl₄ has an optical band gap of 2.47 eV and is stable up to 172 °C, while (2A5MP)₂CuBr₄ has a band gap of 1.66 eV with a stability of up to 185 °C. When Br^- occupies the X site, (2A5MP)₂CuBr₄ exhibits an optical band gap (1.66 eV) close to the optimal value for solar cell absorbers. Furthermore, replacing Cl^- with Br^- enhances thermal stability by 13 °C. Therefore, (2A5MP)₂CuBr₄ demonstrates significant potential as a light-absorbing layer for solar cells.

Semitransparent perovskite solar cells can provide auxiliary power in applications such as power-generating windows and smart car windows. However, in conventional planar-structured devices, both the power conversion efficiency (PCE) and the average visible light transmittance (AVT) of the devices are restricted by the band gap or thickness of the perovskite absorption layer, which hinders the development and application of semitransparent perovskite solar cells. In this work, we construct a new type of semitransparent perovskite solar cell with a three-dimensional (3D) mesh structure using nickel mesh as a framework and bottom electrode. The AVT of the device is controlled by a nickel mesh. When narrow band gap perovskite materials were deposited, the PCE of the device was 4.48%, the average visible light transmittance was 16.5%, the color rendering index was 98.35, and the bifacial coefficient reached 79%. Additionally, due to the flexible nature of the nickel mesh, the device exhibited excellent mechanical stability, maintaining 90% of its initial PCE after 1000 bending cycles at R = 10 mm. This three-dimensional mesh structure provides a new idea for realizing the transmittance of semitransparent flexible perovskite solar cells with high efficiency and high transmittance. It is expected to promote their wide application in fields such as building-integrated photovoltaics.

Sticker-type transparent antireflective film (STAF) is applied to perovskite solar cells (PSCs) to reduce the reflection and improve the light-trapping ability of PSCs. However, the development of STAF is hindered by many factors, such as expensive materials, low actual service life, unsatisfactory antireflective effect, and a lack of research on stability. This work proposes an ultraviolet (UV)-resistant enhanced sticker-type nanostructure acrylic resin antireflective film (SNAAF), which is applied to the incident surface of PSCs. SNAAF is prepared by using a cleverly designed two-step peeling transfer process. The average reflectance of the related device is reduced by 4.06% through the entire visible light spectrum, which also helps achieve the champion performance of the PSCs with STAF. The excellent antireflection performance increases power conversion efficiency (PCE) from 20.77% to 22.1% owing to the significantly enhanced short-circuit current density by 5.5% with the SNAAF. Additionally, the target device maintains nearly 80% of its initial PCE after 480 h of irradiation with UV light (365 nm), far exceeding the exposure levels in IEC 61215. Moreover, the designed SNAAF is applicable to large-area Cu(In, Ga)Se₂ (CIGS) solar cells (area: 225 cm²), which develops a practical external engineering strategy for optimizing device performance for different types of commercial solar cells.

The post-treatment based on spin-coating (SC) organic amine salts is commonly used for surface modification of perovskite films to eliminate defects. However, there is still a lack of systematic study and a unified understanding of the functions and mechanisms of different organic amine salts. The SC method is also not conducive to the industrialization of solar cells. In this work, we study three different organic amine salts, and a passivation strategy for perovskite films based on green anisole liquid soaking (ALS) has been developed. Phenylethylammonium iodide (PEAI), diethylamine hydroiodide (DEAI), and guanidine hydroiodide (GAI) organic amine salt passivators are selected to modify perovskite films, and their effect and working mechanism are also systematically estimated. It is found that PEAI passivates shallow-level defects on the surface of perovskite films, while DEAI incorporates into the perovskite lattice to suppress point defects, and GAI eliminates excess PbI2 residuals in perovskite films. These three organic-amine-salt-modified devices achieve enhanced power conversion efficiencies (PCE) of 21.82% (PEAI-ALS), 21.74% (DEAI-ALS), and 22.21% (GAI-ALS), which is much higher than that of the pristine device without treatment (19.95%). The PCE of the PEAI-ALS device retains nearly 94% of the initial efficiency after 1200 h in unpackaged conditions and about 40% ambient humidity, achieving the best stability performance. Particularly, the PEAI-ALS device has the best comprehensive performance in efficiency and stability. And PEAI is estimated by the SC method and ALS method, and it is found that the PEAI-ALS device achieves a higher PCE compared to the PEAI-SC device (21.51%). We believe that the post-treatment based on a combination of appropriate amine salts and ALS enables a universal approach for fabrication of perovskite solar cells with enhanced photovoltaic performance.