In Situ Unveiling of the Resistive Switching Mechanism of Halide Perovskite-Based Memristors.

The organic-inorganic halide perovskite has become one of the most promising candidates for next-generation memory devices, i.e. memristors, with excellent performance and solution-processable preparation. Yet, the mechanism of resistive switching in perovskite-based memristors remains ambiguous due to a lack of in situ visualized characterization methods. Here, we directly observe the switching process of perovskite memristors with in situ photoluminescence (PL) imaging microscopy under an external electric field. Furthermore, the corresponding element composition of conductive filaments (CFs) is studied, indicating that the metallic CFs with respect to the activity of the top electrode are essential for device performance. Finally, electrochemical impedance spectroscopy (EIS) is conducted to reveal that the transition of ion states is associated with the formation of metallic CFs. This study provides in-depth insights into the switching mechanism of perovskite memristors, paving a pathway to develop and optimize high-performance perovskite memristors for large-scale applications.

Operando dynamics of trapped carriers in perovskite solar cells observed via infrared optical activation spectroscopy.

Conventional spectroscopies are not sufficiently selective to comprehensively understand the behaviour of trapped carriers in perovskite solar cells, particularly under their working conditions. Here we use infrared optical activation spectroscopy (i.e., pump-push-photocurrent), to observe the properties and real-time dynamics of trapped carriers within operando perovskite solar cells. We compare behaviour differences of trapped holes in pristine and surface-passivated FA0.99Cs0.01PbI3 devices using a combination of quasi-steady-state and nanosecond time-resolved pump-push-photocurrent, as well as kinetic and drift-diffusion models. We find a two-step trap-filling process: the rapid filling (~10 ns) of low-density traps in the bulk of perovskite, followed by the slower filling (~100 ns) of high-density traps at the perovskite/hole transport material interface. Surface passivation by n-octylammonium iodide dramatically reduces the number of trap states (~50 times), improving the device performance substantially. Moreover, the activation energy (~280 meV) of the dominant hole traps remains similar with and without surface passivation.

Paeoniflorin inhibits colorectal cancer cell stemness through the miR-3194-5p/catenin beta-interacting protein 1 axis.

Paeoniflorin (PF) is a natural plant ingredient with remarkable antitumor effects. Herein, we investigated the biological effects and mechanism of PF in colorectal cancer (CRC) cell stemness. The messenger RNA (mRNA) and protein expressions were assessed using quantitative real-time polymerase chain reaction and western blot. The viability, proliferation, and migration and invasion of CRC cells were evaluated using cell counting kit-8, clone-formation, and transwell migration and invasion assays, respectively. The sphere-formation capacity was determined using the sphere-formation assay. A dual-luciferase reporter gene assay was employed to analyze the interaction between miR-3194-5p and catenin beta-interacting protein 1 (CTNNBIP1). The viability, migration, invasion, epithelial-mesenchymal transition, and stemness of CRC cells were repressed by PF. MiR-3194-5p was upregulated in CRC tissues and cells. MiR-3194-5p knockdown suppressed CRC cell stemness, while miR-3194-5p overexpression had the opposite effect. In addition, the inhibition of CRC cell stemness caused by PF was eliminated by miR-3194-5p overexpression. CTNNBIP1 functioned as the target of miR-3194-5p, whose knockdown abrogated the repression of CRC cell stemness and Wnt/ß-catenin signaling activation by PF.PF regulated the miR-3194-5p/CTNNBIP1/Wnt/ß-catenin axis to repress CRC cell stemness.

All-solution-processed perovskite/gallium nitride particles hybrid visible-blind ultraviolet photodetectors.

Last decades have witnessed the rapid development of ultraviolet (UV) photodetectors in diversity of applications. The III-nitride semiconductor and metal halide perovskite have both performed promising UV-sensing optoelectronic properties. However, they are still suffering from either the high temperature epitaxial-growth or low photocurrent generated in UV range. In this work, we demonstrate an innovative MAPbCl3/GaN particle hybrid device with all-solution-processed deposition methods. Comparing to the control MAPbCl3photoconductors, the photo-sensing ability of the hybrid device with the optimal concentration of GaN particles is more than one order of magnitude enhanced, and report a responsivity of 86 mA W-1, a detectivity of 3.1 × 1011Jones and a rise/fall time of 1.1/10.7 ms at 360 nm. The photocurrent increment could be attributed to the enhanced UV absorption of GaN particles and facilitated charge separation and photoconductive gain at MAPbCl3/GaN heterojunction. This work paves a pathway towards the large-scale low-cost UV photodetectors in versatile applications.

Manipulating Ion Migration and Interfacial Carrier Dynamics via Amino Acid Treatment in Planar Perovskite Solar Cells.

Instability caused by the migrating ions is one of the major obstacles toward the large-scale application of metal halide perovskite optoelectronics. Inactivating mobile ions/defects via chemical passivation, e.g., amino acid treatment, is a widely accepted approach to solve that problem. To investigate the detailed interplay, L-phenylalanine (PAA), a typical amino acid, is used to modify the SnO2/MAPbI3 interface. The champion device with PAA treatment maintains 80% of its initial power conversion efficiency (PCE) when stored after 528 h in an ambient condition with the relative humidity exceeding 70%. By employing a wide-field photoluminescence imaging microscope to visualize the ion movement and calculate ionic mobility quantitatively, we propose a model for enhanced stability in perspective of suppressed ion migration. Besides, we reveal that the PAA dipole layer facilitates charge transfer at the interface, enhancing the PCE of devices. Our work may provide an in-depth understanding toward high-efficiency and stable perovskite optoelectronic devices.