Artificial Synapse Based on a δ-FAPbI3/Atomic-Layer-Deposited SnO2 Bilayer Memristor.

Halide perovskite-based resistive switching memory (memristor) has potential in an artificial synapse. However, an abrupt switch behavior observed for a formamidinium lead triiodide (FAPbI3)-based memristor is undesirable for an artificial synapse. Here, we report on the δ-FAPbI3/atomic-layer-deposited (ALD)-SnO2 bilayer memristor for gradual analogue resistive switching. In comparison to a single-layer δ-FAPbI3 memristor, the heterojunction δ-FAPbI3/ALD-SnO2 bilayer effectively reduces the current level in the high-resistance state. The analog resistive switching characteristics of δ-FAPbI3/ALD-SnO2 demonstrate exceptional linearity and potentiation/depression performance, resembling an artificial synapse for neuromorphic computing. The nonlinearity of long-term potentiation and long-term depression is notably decreased from 12.26 to 0.60 and from -8.79 to -3.47, respectively. Moreover, the δ-FAPbI3/ALD-SnO2 bilayer achieves a recognition rate of ≤94.04% based on the modified National Institute of Standards and Technology database (MNIST), establishing its potential in an efficient artificial synapse.

Atmospheric Humidity Underlies Irreproducibility of Formamidinium Lead Iodide Perovskites.

Metal halide perovskite solar cells (PSCs) are infamous for their batch-to-batch and lab-to-lab irreproducibility in terms of stability and performance. Reproducible fabrication of PSCs is a critical requirement for market viability and practical commercialization. PSC irreproducibility plagues all levels of the community; from institutional research laboratories, start-up companies, to large established corporations. In this work, the critical function of atmospheric humidity to regulate the crystallization and stabilization of formamidinium lead triiodide (FAPbI3) perovskites is unraveled. It is demonstrated that the humidity content during processing induces profound variations in perovskite stoichiometry, thermodynamic stability, and optoelectronic quality. Almost counterintuitively, it is shown that the presence of humidity is perhaps indispensable to reproduce phase-stable and efficient FAPbI3-based PSCs.

Effects of MgF2anti-reflection coating on optical losses in metal halide perovskite solar cells.

The importance of light management for perovskite solar cells (PSCs) has recently been emphasized because their power conversion efficiency approaches their theoretical thermodynamic limits. Among optical strategies, anti-reflection (AR) coating is the most widely used method to reduce reflectance loss and thus increase light-harvesting efficiency. Monolayer MgF2is a well-known AR material because of its optimal refractive index, simple fabrication process, and physical and chemical durabilities. Nevertheless, quantitative estimates of the improvement achieved by the MgF2AR layer are lacking. In this study, we conducted theoretical and experimental evaluations to assess the AR effect of MgF2on the performance of formamidinium lead-triiodide PSCs. A sinusoidal tendency to enhance the short-circuit current density (JSC) was observed depending on the thickness, which was attributed to the interference of the incident light. A transfer matrix method-based simulation was conducted to calculate the optical losses, demonstrating the critical impact of reflectance loss on theJSCimprovement. The predictedJSCs values, depending on the perovskite thickness and the incident angle, are also presented. The combined use of experimental and theoretical approaches offers notable advantages, including accurate interpretation of photocurrent generation, detailed optical analysis of the experimental results, and device performance predictions under unexplored conditions.

Enhancing Efficiency and Stability of Tin Halide Perovskite Light-Emitting Diodes via Engineered Alkali/Multivalent Metal Salts.

Sn-based perovskite light-emitting diodes (PeLEDs) have emerged as promising alternatives to Pb-based PeLEDs with their rapid increase in performance owing to the various research studies on inhibiting Sn oxidation. However, the absence of defect passivation strategies for Sn-based perovskite LEDs necessitates further research in this field. We performed systematic studies to investigate the design rules for defect passivation agents for Sn-based perovskites by incorporating alkali/multivalent metal salts with various cations and anions. From the computational and experimental analyses, sodium trifluoromethanesulfonate (NaTFMS) was found to be the most effective passivation agent for PEA2SnI4 films among the explored candidate agents owing to favorable reaction energetics to passivate iodide Frenkel defects. Consequently, the incorporation of NaTFMS facilitates the formation of uniform films with relatively large crystals and reduced Sn4+. The NaTFMS-containing PEA2SnI4 PeLEDs demonstrate an improved luminance of 138.9 cd/m2 and external quantum efficiency (EQE) of 0.39% with an improved half-lifetime of more than threefold. This work provides important insight into the design of defect passivation agents for Sn-based perovskites.

Rational Design of a Chemical Bath Deposition Based Tin Oxide Electron-Transport Layer for Perovskite Photovoltaics.

Chemical bath deposition (CBD) is widely used to deposit tin oxide (SnOx ) as an electron-transport layer in perovskite solar cells (PSCs). The conventional recipe uses thioglycolic acid (TGA) to facilitate attachments of SnOx particles onto the substrate. However, nonvolatile TGA is reported to harm the operational stability of PSCs. In this work, a volatile oxalic acid (OA) is introduced as an alternative to TGA. OA, a dicarboxylic acid, functions as a chemical linker for the nucleation and attachment of particles to the substrate in the chemical bath. Moreover, OA can be readily removed through thermal annealing followed by a mild H2 O2 treatment, as shown by FTIR measurements. Synergistically, the mild H2 O2 treatment selectively oxidizes the surface of the SnOx layer, minimizing nonradiative interface carrier recombination. EELS (electron-energy-loss spectroscopy) confirms that the SnOx surface is dominated by Sn4+ , while the bulk is a mixture of Sn2+ and Sn4+ . This rational design of a CBD SnOx layer leads to devices with T85 ≈1500 h, a significant improvement over the TGA-based device with T80 ≈250 h. The champion device reached a power conversion efficiency of 24.6%. This work offers a rationale for optimizing the complex parameter space of CBD SnOx to achieve efficient and stable PSCs.

Suppressing ion migration in metal halide perovskite via interstitial doping with a trace amount of multivalent cations.

Cations with suitable sizes to occupy an interstitial site of perovskite crystals have been widely used to inhibit ion migration and promote the performance and stability of perovskite optoelectronics. However, such interstitial doping inevitably leads to lattice microstrain that impairs the long-range ordering and stability of the crystals, causing a sacrificial trade-off. Here, we unravel the evident influence of the valence states of the interstitial cations on their efficacy to suppress the ion migration. Incorporation of a trivalent neodymium cation (Nd3+) effectively mitigates the ion migration in the perovskite lattice with a reduced dosage (0.08%) compared to a widely used monovalent cation dopant (Na+, 0.45%). The photovoltaic performances and operational stability of the prototypical perovskite solar cells are enhanced with a trace amount of Nd3+ doping while minimizing the sacrificial trade-off.

Multiplane Facelift Following Facial Bone Contouring for Enhanced Mobilization and Rejuvenation.

INTRODUCTION: The aging process is inevitable in life, and the social demand for rejuvenation increases by year. The face acquires both soft tissue and skeletal changes through aging, and correcting only one side has limits in natural rejuvenation. Thus, the authors combined multiplane facelift with whole-facial bone contouring for maximal results. METHODS: From March 2017 to February 2019, a total of 22 patients received multiplane facelift following facial bone contouring in our institute. The authors retrospectively reviewed information on demographics, surgical procedure, complications, and satisfaction. Under general anesthesia, the patient received reduction malarplasty, genioplasty, and mandible anglectomy via intraoral incisions, and multiplane facelift through retrotragal and postauricular incisions. RESULTS: All patients were females with the mean age of 42.86 ±â€Š9.55. The mean operation time was 296.39 ±â€Š31.87 minutes and the mean follow-up period was 12.59 ±â€Š6.77 months. Few complications included hematoma and unfavorable scars. More than 95% of the patients were very satisfactory with the result. CONCLUSION: In this study, the authors present our novel procedure of combining whole-facial bone contouring and multiplane facelift. This technique can reestablish the facial skeletal foundation and effectively lift soft tissues in various vectors with longevity and safety.

Long-term stable, low-temperature remote silicate phosphor thick films printed on a glass substrate.

A critical step in providing better phosphor solution for white light emitting diode (LED) is to utilize inexpensive silicate phosphors with strong thermal stability. Here, we demonstrate yellow silicate phosphor-embedded glass thick films with a high luminous efficacy of ∼32 lm/W at 200 mA as a nonconventional remote-phosphor approach. The simple screen-printing process of a paste consisting of (Ba,Sr,Ca)2SiO4:Eu²âº phosphor and a low softening point glass creates a planar remote structure on a regular soda lime silicate glass with controllable film thickness and location (top vs bottom) of the phosphor layer. The glass matrix provides promising densification and adhesion with the substrate at the optimal low temperature of 410 °C, with the long-term stability in luminous efficacy over 500 h of operation. The proposed phosphor structure has important implications to overcome current limitations as phosphors.

Perineal reconstruction using a bilobed pudendal artery perforator flap.

BACKGROUND: To reconstruct the perineal region, including the urogenital and anal triangle that differ from each other in tissue characteristics and function, we applied pudendal artery perforator flaps with a bilobed flap design. This bilobed flap design could improve the arc of flap rotation and the mobility of the flap so it could cover wide and deep defects. Moreover, it could preserve the characteristics of each triangle. METHODS: This study enrolled a total of 15 female patients who had undergone perineal reconstruction with pudendal artery perforator flaps. Seven of them had vulva cancer, seven others had extramammary Paget's disease and the remaining one patient had rectovaginal fistula. We examined the location and shape of the defects, flap designs and their clinical courses. RESULTS: All flaps survived during the entire follow-up period. The flap sizes ranged from 3x4 to 13x12 cm, and the follow-up period was 4.6 months on average. Bilobed flaps were used in nine patients, and unilobed flaps were used in six patients. The reconstructed areas were in good functional and aesthetic conditions. CONCLUSION: We used a bilobed pudendal artery perforator flap according to the location and shape of defect areas in the perineal region. As a result, we could preserve the functional, morphological and cosmetic characteristics of the defect areas.

Vomopalatoplasty: a novel procedure to reduce velopharyngeal distance in cleft palate repair.

Despite numerous improvements in the palatoplasty procedure, speech dysfunction tends to develop in many patients, requiring another surgery. In addition, vomer flaps have been used in palatoplasty in various shapes and on purposes. Nonetheless, they have been used mostly to cover the defect in wide and complete type of cleft palate. We introduce the vomopalatoplasty procedure that uses a vomer flap to reduce the nasopharyngeal space in incomplete or submucous type of cleft palate patients.The mucoperiosteal flaps on the nasal and oral sides were elevated by the conventional palatoplasty procedure, which subsequently elevated the bilateral vomer flaps to the posterior edge of vomer. Then, the vomer flap was sutured with the mucoperiosteal flap of the nasal side to the anterior half of the soft palate, and thus, the soft palate was fixed in more posterosuperior direction than in conventional palatoplasty. For patients whose junction of vomer and hard palate had to be exposed, a part of the bone at the bifid posterior nasal spine of the hard palate may be removed sometimes.Ostectomy of the bifid posterior nasal spine or the posterior end of the hard palate was performed in 11 patients. Another 12 patients did not need ostectomy. After the surgery, the surgical wounds healed well in all patients without any major complications such as dehiscence or loss of flap.Our vomopalatoplasty is easy to perform, and the procedure could be combined to the conventional palatoplasty procedure. Thus, we consider vomopalatoplasty as a useful procedure that could reduce the nasopharyngeal space in patients with incomplete or submucous type of cleft palate.