Instability in CH3NH3PbI3 perovskite solar cells due to elemental migration and chemical composition changes

Organic-inorganic halide perovskites have rapidly grown as favorable materials for photovoltaic applications, but accomplishing long-term stability is still a major research problem. This work demonstrates a new insight on instability and degradation factors in CH3NH3PbI3 perovskite solar cells aging with time in open air. X-ray photoelectron spectroscopy (XPS) has been used to investigate the compositional changes caused by device degradation over the period of 1000 hrs. XPS spectra confirm the migration of metallic ions from the bottom electrode (ITO) as a key factor causing the chemical composition change in the perovskite layer besides the diffusion of oxygen. XPS results are in good agreement with the crystallographic marks. Glow discharge optical emission spectrometry (GD-OES) has also been performed on the samples to correlate the XPS results. Based on the experimental results, fundamental features that account for the instability in the perovskite solar cell is discussed. - 2017 The Author(s).The authors are thankful to the Center for Advanced Materials (CAM), Qatar University for the laboratory support during the experimental work. The authors are also grateful to the Gas Processing Center (GPC), Qatar University for providing the XPS analysis facility. Thanks to HORIBA Scientific – Jocelyne Marciano, Sofia Gaiaschi and Patrick Chapon for the GD measurements and interpretation. This publication was also made possible by NPRP grant # 6-175-2-070 from Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

A short analysis on the morphological characterization of colloidal quantum dots for photovoltaic applications

Due to its various advantages, colloidal quantum dots (CQDs) carry a prodigious deal of interest in low-cost photovoltaics. The possibility of tailored band gaps via quantum confinement effect facilitates photovoltaic devices to be tuned to allow their optical absorption bandwidths to match with the solar spectrum. Size, shape, and material composition are some of the significant factors which affect the optical and electronic properties of QDs. Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) are some of the most resourceful methods available for the microstructural characteristics of solid materials. These techniques can provide useful information about the structural, morphological and compositional properties of the specimen. In this focused review, we analyze the several types of QDs, their synthesis and characterization, exclusively morphological studies carried out on quantum dots for solar cell applications. Despite various advantages and techniques used for morphological characterization of QDs, very few reviews are reported in the past years. In this review, we have compiled the important and latest findings published on morphological analysis of QDs for photovoltaic applications which can provide the guideline for the research for the future work in the field.Scopu

A novel classification of prostate specific antigen (PSA) biosensors based on transducing elements

During the last few decades, there has been a tremendous rise in the number of research studies dedicated towards the development of diagnostic tools based on bio-sensing technology for the early detection of various diseases like cardiovascular diseases (CVD), many types of cancer, diabetes mellitus (DM) and many infectious diseases. Many breakthroughs have been developed in the areas of improving specificity, selectivity and repeatability of the biosensor devices. Innovations in the interdisciplinary areas like biotechnology, genetics, organic electronics and nanotechnology also had a great positive impact on the growth of bio-sensing technology. As a product of these improvements, fast and consistent sensing policies have been productively created for precise and ultrasensitive biomarker-based disease diagnostics. Prostate-specific antigen (PSA) is widely considered as an important biomarker used for diagnosing prostate cancer. There have been many publications based on various biosensors used for PSA detection, but a limited review was available for the classification of these biosensors used for the detection of PSA. This review highlights the various biosensors used for PSA detection and proposes a novel classification for PSA biosensors based on the transducer type used. We also highlight the advantages, disadvantages and limitations of each technique used for PSA biosensing which will make this article a complete reference tool for the future researches in PSA biosensing.Scopu

Effect of ambient temperature on the efficiency of the PCPDTBT: PC71BM BHJ solar cells

In this research article, the influence of environment temperature on the performance of the organic bulk heterojunction organic solar cells has been investigated. We describe the effect of ambient temperature on the efficiency of poly-[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta-[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and [6, 6]-phenylC71-butyric-acid-methyl-ester (PC71BM)-based bulk heterojunction (BHJ) organic solar cells. The current–voltage characteristics of the ITO/PEDOT:PSS/PCPDTBT:PC71BM/Al solar cells are recorded in the temperature range of 25–60 °C under 100 mW/cm2 solar irradiation. The short-circuit current (J sc) of the solar cells increased from 4.28 to 9.23 mAcm−2 when the temperature elevated from 25 to 55 °C. However, the open-circuit voltage (V oc) and fill factor (FF) of the cells almost remained unchanged over the whole investigated temperature range. The values of V oc and FF are found to be 0.58 ± 01 and 0.60 ± 0.12 V, respectively. The results clearly indicate that the maximum efficiency of the ITO/PEDOT:PSS/PCPDTBT:PC71BM/Al solar cells can be achieved in the range of 52–58 °C.This publication was made possible by PDRA Grant No. PDRA1-0117-14109 from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors.Scopu

Synthesis and Characterization of Magnetic Nanostructured Lipid Carriers (mNLCs) for Drug Delivery

Magnetic nanoparticles (MNPs) are a class of nanoparticles, which can be manipulated using magnetic fields. Currently, MNPs are recognized as one of the most important mode as a drug carrier while they can also be potentially used as carriers for gene delivery. In this article, magnetic nanostructured lipid carriers (mNLCs) are prepared through co-precipitation method. The particle size and zeta potential, structure and thermal properties of the MNPS have been studied. The produced MNPs were also hydrophobically modified with a long chain of fatty acid namely lauric acid. These modified MNPs were mixed with nanostructured lipid carriers (NLCs) to form mNLCs. The heat capacity and flow of mNLCs was profligate in the presence of a magnetic field which is a worthy attribute for targeted drug delivery applications

Influence of relative humidity on the electrical response of PEDOT:PSS based organic field-effect transistor

We have investigated the influence of relative humidity on the electrical response of a bottom gate organic field-effect transistor (OFET) with poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonate) (PEDOT:PSS) as an active channel material. For sensor fabrication, the organic polymer PEDOT:PSS has been spun-cast on highly doped n-Si wafer with preliminary thermally deposited gold, source and drain electrodes. The structural characterization and surface morphology study of active layer has been performed by XRD and FESEM, respectively. From the transfer characteristic curve, the p-type hole conductivity in PEDOT:PSS thin film is confirmed. Whereas from the output current-voltage (I–V) characteristic of the OFET, the Ion/Ioff ratio has been measured to be ∼2.6, when operated at relative humidity (RH) ∼60%. The humidity sensing characteristics of the OFET have further been investigated by exposing the proposed OFET to varied RH levels (40–80% RH) at room temperature (26.2 °C). Within the humidity range examined, the channel current has been observed to amplify by nearly 29.4 times of its magnitude