Properties of Halide Perovskite Photodetectors with Little Rubidium Incorporation

This study investigates the effects of Rb doping on the Rb-formamidinium-methylammonium-PbI3 based perovskite photodetectors. Rb was incorporated in the perovskite films with different contents, and the corresponding photo-response properties were studied. Doping of few Rb (~2.5%) was found to greatly increase the grain size and the absorbance of the perovskite. However, when the Rb content was greater than 2.5%, clustering of the Rb-rich phases emerged, the band gap decreased, and additional absorption band edge was found. The excess Rb-rich phases were the main cause that degraded the performance of the photodetectors. By space charge limit current analyses, the Rb was found to passivate the defects in the perovskite, lowering the leakage current and reducing the trap densities of carriers. This fact was used to explain the increase in the detectivity. To clarify the effect of Rb, the photovoltaic properties were measured. Similarly, h perovskite with 2.5% Rb doping increased the short-circuit current, revealing the decline of the internal defects. The 2.5% Rb doped photodetector showed the best performance with responsivity of 0.28 AW−1 and ~50% quantum efficiency. Detectivity as high as 4.6 × 1011 Jones was obtained, owing to the improved crystallinity and reduced defects.

Forensic Camera Identification in Social Networks via Camera Fingerprint

Image-related crimes cause the urgent demand for tracing the origin of digital images. The breakthrough is a passive detection method via photo response non-uniformity (PRNU) analysis proposed by Lukáš et al. Recently, digital images are often shot with handheld devices (such as smartphones) and transmitted using social media (such as LINE). Most of the images are distorted (such as compressed and resized) during transmission. Previous studies are less focused on the impact of transmission compression through social networks. Thirty-one different Apple mobile phones were used to capture digital images in the experiment. Images were uploaded to the photo album via LINE software and then downloaded. The modified signed peak correlation energy (MSPCE) statistics is used to evaluate the correlation between the PRNU values of the disputed images and the pattern noise of the experimental devices. Experimental results show that the PRNU analysis method can effectively trace the source of the shot device using the distorted images which are compressed and resized during the transmission in LINE.

A comprehensive non-uniformity correction method for EMCCD

The non-uniformity of image directly affects the application of EMCCD in various disciplines. The proposed method can significantly improve the uniformity of EMCCD output image. The correction algorithm of "reverse split and forward recovery" is determined through analyzing the imaging model of EMCCD, and the comprehensive non-uniformity correction function model is established. The 8-tap EMCCD chip CCD220 of British e2v company is used for experimental verification. The results show that after the comprehensive correction the consistencies of the light response characteristic curve and the multiplication gain curve of each channel in EMCCD are obviously improved, and also the photo response non-uniformity (PRNU) of the output image is substantially reduced from 24.5 to 4.1%, which prove the effectiveness of the proposed method.

Solar Energy as Renewable Energy for the Degradation of Pollutants using High Active Ag@TiO2/α-Fe2O3 Ternary Nanocomposite Photocatalyst

In this work, ternary Ag@TiO2/α-Fe2O3 nanocomposite were synthesized via solvothermal chemical reduction method using N,N-dimethylformamide (DMF) as solvent and reducing agent. The chemical procedure involves the use of only metals precursors without the need to use any other surfactants or capping agents. Physicochemical properties of the designed photocatalyst are found by means of various modern techniques. XRD data confirmed the high crystallinity of the obtained ternary nanocomposite. On the other hand, using TEM and HRTEM instruments, the shape and morphology of the Ag@TiO2/α-Fe2O3 nanocomposite were found to be spherical with an average particle size of 150 nm. The UV-Vis measurement shows that Ag@TiO2/α-Fe2O3 as photocatalyst exhibited good photo response in the visible region. The effect of preparation method and the performance of the designed photocatalyst were evaluated by photodegradation measurements of MB under visible light irradiation. We observed that the combination of metallic silver nanoparticles (AgNPs) and hematite iron oxide (α-Fe2O3) with titanium dioxide (TiO2) enhance the photocatalytic activity of the ternary Ag@TiO2/α-Fe2O3 photocatalyst compared to bare TiO2 suggesting its potential for many purification applications.

Dynamics of light-induced charge transfer between carbon nanotube and CdSe/CdS core/shell nanocrystals

The integration of semiconducting colloidal nanocrystals (NCs) with carbon nanotubes (CNTs) in a single device presents a unique platform that combines optical flexibility with high charge carrying capability. These qualities are desirable in many applications such as photovoltaic cells, photocatalysis, and light sensors. Here, we present hybrid devices that incorporate various CdSe/CdS core/shell NCs, such as seeded quantum dots (sQDs) and asymmetric seeded nanorods (a-sNRs), with single-wall carbon nanotube in a field-effect transistor geometry. We used electrical measurements to probe a light-induced charge transfer (LICT) between the CdSe/CdS NCs and the CNT. We investigate the effect of gate voltage on the LICT magnitude and temporal characteristics. Surprisingly, the measured photo-response depends on the gate voltage, and we observe both electrons and holes transfer from the a-sNRs to the CNT. Furthermore, comparison between LICT measurements on different devices with different CNTs and NC types reveals that the charge transfer time is directly proportional to the shell-thickness around the CdSe core and inversely correlated with the NCs size. The recovery of the charge trapped inside the CdSe/CdS NCs is characterized by two distinct fast and slow relaxation times, which depend on the NCs size and CNT type. Although, the charge relaxation time is similar between the symmetric QDs and the asymmetric sNRs, the overall percentage of the remaining charge in the QDs is significantly larger than in the sNRs. Understanding both gate voltage and NCs size effect on the LICT processes can assist to optimize the performance of optoelectronic devices.

Negative series resistance and photo-response properties of Au/PPY-MWCNTs composite /TiO2/Al2O3/n-Si/Al photodiode

The paper addresses a novel approach concerning the appearance of negative series resistance (Rs) at high frequencies for both temperatures and voltages. Most of the previous studies have focused on the relationship between voltage and current (I - V) to determine the value of Rs using several methods. By measuring capacitance and conductance as a function of voltage, we were able to develop a systematic analysis of series resistance. At high frequencies of 2×107, 107 Hz, Rs has negative values however, at frequency 106Hz it takes both positive and negative values, whilst from (105 - 10) Hz it has positive values. Here in this article, we synthesized Au/PPY-MWCNTs/TiO2/Al2O3/n-Si/Al structure which can be used in a variety of applications such as supercapacitors, and diodes. We investigated the electrical properties such as ideality factor (n), barrier height (фb), series resistance using several approaches such as conventional, Chueng, and Nord methods. The structure has shown rectification with a good response to daylight illumination. The structure response to daylight illumination indicates that photodiodes have the potential to be used as solar detectors.

Spectral responses across a dorsal–ventral array of dermal sensilla in the medicinal leech

How do animals use visual systems to extract specific features of a visual scene and respond appropriately? The medicinal leech, Hirudo verbana, is a predatory, quasi-amphibious annelid with a rich sensorium that is an excellent system in which to study how sensory cues are encoded, and how key features of visual images are mapped into the CNS. The leech visual system is broadly distributed over its entire body, consisting of five pairs of cephalic eyecups and seven segmentally iterated pairs of dermal sensilla in each mid-body segment. Leeches have been shown to respond behaviorally to both green and near ultraviolet light (UV, 365–375 nm). Here, we used electrophysiological techniques to show that spectral responses by dermal sensilla are mapped across the dorsal–ventral axis, such that the ventral sensilla respond strongly to UV light, while dorsal sensilla respond strongly to visible light, broadly tuned around green. These results establish how key features of visual information are initially encoded by spatial mapping of photo-response profiles of primary photoreceptors and provide insight into how these streams of information are presented to the CNS to inform behavioral responses.