Search

The photovoltaic performances of n-i-p or inverted p-i-n BaSi2 homojunction solar cells are limited by the parasitic high light absorption of n-BaSi2 or p-BaSi2 window layer. In this work, diverse electron transport materials (ETMs) and hole transport materials (HTMs) are employed instead of BaSi2 as window layers to promote the performances of BaSi2 solar cells, and the effects of different ETMs and HTMs were simulated and comprehensively studied. For n-ETM/i-BaSi2/p-BaSi2 solar cells, the solar cell with ZnO exhibits the highest efficiency of 28.21%. As increasing the thicknesses of ETM layer from 5 nm to 100 nm, the efficiency for n-BaSi2/i-BaSi2/p-BaSi2 solar cell decreases seriously from 24.52% to 15.99%, while the solar cells with wide band gap ETMs including SnO2, TiO2 and ZnO show neglectable change in performances. The performances n-ETM/i-BaSi2/p-BaSi2 solar cells are affected by donor like defects more than acceptor like defects in i-BaSi2. For p-HTM/i-BaSi2/n-BaSi2 solar cells, employing Cu2O, CuI, CuSCN or NiO as HTM layer produces evident valence band discrepancies at HTM/i-BaSi2 interfaces. Heavy doping in HTM layer is necessary desired to overcome the energy band barriers. As increasing the thicknesses of HTM layer from 5 nm to 100 nm, the efficiency for p-BaSi2/i-BaSi2/n-BaSi2 solar cell also decreases from 24.52% to 15.99%, while the solar cells with wide band gap HTMs including CuI, CuSCN and NiO show neglectable change, and the efficiency for p-Cu2O/i-BaSi2/n-BaSi2 solar cells decreases slightly from 25.86% to 24.88%. The performances of p-HTM/i-BaSi2/n-BaSi2 solar cells are affected by acceptor like defects more than donor like defects in i-BaSi2. [ABSTRACT FROM AUTHOR]

The interest in video anomaly detection systems that can detect different types of anomalies, such as violent behaviours in surveillance videos, has gained traction in recent years. The current approaches employ deep learning to perform anomaly detection in videos, but this approach has multiple problems. For example, deep learning in general has issues with noise, concept drift, explainability, and training data volumes. Additionally, anomaly detection in itself is a complex task and faces challenges such as unknownness, heterogeneity, and class imbalance. Anomaly detection using deep learning is therefore mainly constrained to generative models such as generative adversarial networks and autoencoders due to their unsupervised nature; however, even they suffer from general deep learning issues and are hard to properly train. In this paper, we explore the capabilities of the Hierarchical Temporal Memory (HTM) algorithm to perform anomaly detection in videos, as it has favorable properties such as noise tolerance and online learning which combats concept drift. We introduce a novel version of HTM, named GridHTM, which is a grid-based HTM architecture specifically for anomaly detection in complex videos such as surveillance footage. We have tested GridHTM using the VIRAT video surveillance dataset, and the subsequent evaluation results and online learning capabilities prove the great potential of using our system for real-time unsupervised anomaly detection in complex videos. [ABSTRACT FROM AUTHOR]

In just a few years, the efficiency of perovskite-based solar cells (PSCs) has risen to 25.8%, making them competitive with current commercial technology. Due to the inherent advantage of perovskite thin films that can be fabricated using simple solution techniques at low temperatures, PSCs are regarded as one of the most important low-cost and mass-production prospects. The lack of stability, on the other hand, is one of the major barriers to PSC commercialization. The goal of this review is to highlight the most important aspects of recent improvements in PSCs, such as structural modification and fabrication procedures, which have resulted in increased device stability. The role of different types of hole transport layers (HTL) and the evolution of inorganic HTL including their fabrication techniques have been reviewed in detail in this review. We eloquently emphasized the variables that are critical for the successful commercialization of perovskite devices in the final section. To enhance perovskite solar cell commercialization, we also aimed to obtain insight into the operational stability of PSCs, as well as practical information on how to increase their stability through rational materials and device fabrication. [ABSTRACT FROM AUTHOR]

Perovskite Solar Cells (PSCs) being the most advanced photovoltaic technology today have attracted global attention due to its solution processability and cost effectiveness. In this paper, we reported the performance of perovskite solar cells by integrating Reduced Graphene Oxide (rGO) as a buffer layer. The combined effect of Ultraviolet visible (UV-vis) spectroscopy, X-ray Diffractometer (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Four Point Probe and Solar Simulator were used to explore the absorbance, crystallinity, morphological, resistivity and current voltage behavior of the photoanodes and devices. The rGO was deposited on top the mesoporous Titanium dioxide (m-TiO2) (Device B), on methylammonium lead triiodide (CH3NH3PbI3) perovskite absorber (Device C) and on m-TiO2 & CH3NH3PbI3 perovskite absorber (Device D). The reference device (Device A) was fabricated without rGO as a bench mark for comparison. From the results obtained, the devices with rGO show significant improvement over the device lacking rGO. The reference device gave a Short Circuit Current Density (Jsc) of 8.151 mAcm-2, Open Circuit Voltage (Voc) of 0.575 V, Fill Factor (FF) of 74.4 % and Power Conversion Efficiency (PCE) of 3.49 %. The best performing device was the one with rGO incorporated on both m-TiO2 and CH3NH3PbI3. The device gave a Jsc of 8.737 mAcm-2, Voc of 0.836 V, FF of 68.1% and PCE of 4.98 %. The device experienced an enhancement of ~7.20 % and 42.69 % in Jsc and PCE over the pristine device. This investigation aids the fundamental understanding of the effect of Graphene Materials (GRMs) on the optoelectronic properties of PSCs, and it further confirms the promising prospects of achieving low-cost, efficient and stable PSCs for commercialization with graphene materials. [ABSTRACT FROM AUTHOR]

An ultimate goal of placing fire detection systems in buildings and structures is to allow for the rapid detection of fire and accurate faster than real time prediction of ensuing fire behavior so that relevant information can be delivered to the appropriate stakeholders. In the near-term, development of detection systems with decreased detection time, better discrimination against nuisance and false alarms, and real-time monitoring of the fire state is a critical interim step. Building comfort and efficiency systems are increasingly incorporating a greater quantity of sensors and these sensors are installed at a greater density than any fire sensor with the exception of the sprinkler. While currently used primarily for building management purposes, the application of these, or similar types of building sensors, for rapid fire detection, fire state determination, and fire forecasting offers great potential. This paper discusses the potential benefits of the application of Hierarchical Temporal Memory algorithms for fire state determination in a continuous learning environment based on its application to a series of live fire experiments. [ABSTRACT FROM AUTHOR]

The impact of a significantly lower ferric (Fe3+) ion concentration on the structural, morphological, optical, and electrochemical properties of spin-coated Fe x Ni 1-x O thin films cast on Indium Tin Oxide (ITO) glasses was scrutinized and then compared with a higher ferric (Fe3+) ion concentration. After a careful structural study of the Fe x Ni 1-x O thin films by X-ray diffraction (XRD) analysis, the film surface was further analyzed by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM) study, and X-ray photoelectron spectroscopy (XPS). Even for a noticeably small amount of substituted Ni2+ metal cations by Fe3+, degradation of the host crystal lattice was surprisingly higher. The influence of Fe3+ ions on the optical properties of Fe x Ni 1-x O ITO thin films was studied using UV–visible absorption spectra and Raman spectra. Both unsubstituted and Fe-substituted NiO ITO thin films showed photoluminescence properties. Changes in resistance values in pristine and Fe x Ni 1-x O thin films were monitored by an electrochemical impedance spectroscopy (EIS) study. Fe-substituted NiO thin films with a lower molar concentration showed better electrochemical performance as compared to those with a higher molar concentration of Fe3+ ions. This fact was further reinforced through a current-voltage (IV) study and a cyclic-voltagram (CV) study. [Display omitted] • Fe3+ substituted non-stoichiometric Fe x Ni 1-x O thin films using spin coating. • Minimum Fe3+ substitution in NiO triggering significant structural modification. • PL emission indicating metal defect formation during Fe3+ substitution. • Nickel vacancy defects inducing hole-driven conductivity upon minute Fe3+. [ABSTRACT FROM AUTHOR]

• A bio-inspired learning system for trajectory anomaly detection is proposed. • The method is tested on 2D object trajectories and 3D air signature verification. • An ELM-HTM fusion framework is used. Artificial intelligent systems often model the solutions of typical machine learning problems, inspired by biological processes, because of the biological system is faster and much adaptive than deep learning. The utility of bio-inspired learning methods lie in its ability to discover unknown patterns, and its less dependence on mathematical modeling or exhaustive training. In this paper, we propose a new bio-inspired learning model for a single-class classifier to detect abnormality in video object trajectories. The method uses a simple but dynamic extreme learning machine (ELM) and hierarchical temporal memory (HTM) together referred to as ELM-HTM in an unsupervised way to learn and classify time series patterns. The method has been tested on trajectory sequences in traffic surveillance to find abnormal behaviors such as high-speed, unusual stops, driving in wrong directions, loitering, etc. Experiments have also been performed with 3D air signatures captured using sensors and used for biometric authentication(forged/genuine). The results indicate a significant gain over training time and classification accuracy. The proposed method outperforms in predicting long-time patterns by observing small steps with an average accuracy gain of 15% as compared to the state-of-the-art HTM. The method has applications in detecting abnormal activities in videos by learning the movement patterns as well as in biometric authentication. [ABSTRACT FROM AUTHOR]

Recurrent Neural Networks such as Long Short-Term Memory (LSTM) and Gated Recurrent Units (GRUs) are often deployed as neural network-based predictors for time series data. Recently, Hierarchical Temporal Memory (HTM), a machine learning technology attempting to simulate the human brain's neocortex, has been proposed as another approach to time series data prediction. While HTM has gained a lot of attention, little is known about the actual performance compared to the more common RNNs. The only performance comparison between the two, performed at the company behind HTM, shows they perform similarly. In this article, we present a more in-depth performance comparison, involving more extensive hyperparameter tuning and evaluation on more scenarios. Surprisingly, our results show that both LSTM and GRUs can outperform HTM by over 30% at lower runtime. Furthermore, we show that HTM requires explicitly timestamped data to recognize daily and weekly patterns, while LSTM only needs the raw sequential data to predict such time series accurately. Finally, our experiments indicate that the temporally aware components of all considered predictors contribute nothing to the prediction accuracy. We further strengthen this claim by presenting equally or better performing Multilayer Perceptrons conceptually similar to the HTM and LSTM, disregarding their temporal aspects. [ABSTRACT FROM AUTHOR]

Six materials were used as an interlayer at the anode side (anode interlayer [AIL]) of an archetypical planar heterojunction organic solar cell (OSC). In addition to two conventional wide bandgap hole transport materials (HTMs), tris(4‐carbazol‐9‐ylphenyl)amine (TCTA) and trans‐4,4′‐bis[N‐(naphthalen‐1‐yl)‐N‐phenylamino]stilbene (NPAE), we explore four narrow bandgap materials, bis(biphenylaminospiro)‐fumaronitrile (PhSPFN), bis(N‐(naphthalen‐1‐yl)‐N‐phenylamino)anthraquinone (NPAAnQ), bis‐(di(2‐fluorophenyl)aminospiro)‐fumaronitrile (FPhSPFN), and bis[4‐(N‐(pyren‐1‐yl)‐N‐phenylamino)phenyl]fumaronitrile (PyPAFN), the energy levels of which essentially align with the ones of SubPc, the active light‐absorbing material of the OSC study herein. By using a narrow bandgap AIL, universally enhanced short‐circuit current density and power conversion efficiencies (PCEs) have been achieved. In addition, one of these materials, FPhSPFN, results in a PCE of 5.13%, which is the highest reported value for SubPc solar cells with a similar architecture. This is ascribed to the formation of an otherwise passive exciton‐blocking interface. Furthermore, this demonstrates that charge selectivity by way of a high‐lying lowest unoccupied molecular orbital (LUMO) energy level is not a prerequisite for successful AIL design. As such, in terms of energy level alignment and bandgap energies, we establish a viable alternative approach toward interface and interlayer material design. [ABSTRACT FROM AUTHOR]

The strategy of ion doping in metal oxide is generally used to enhance the photoanode film feature, attain a suitable energy band and enhance carrier mobility. Here, a rare earth element erbium was doped into TiO 2 electron transport layer (ETL) by adding erbium trinitrate into the titanium precursor solution. In the present investigation, an attempt has been made to fabricate perovskite sensitized erbium doped TiO 2 nanoparticle (Er3+@TNPs) photoanode solar cell with different hole transport materials (HTMs) and graphite coated counter electrode. The perovskite sensitized solar cell (PSSC) built with CH 3 NH 3 SnI 3 sensitized Er3+@TNPs photoanode and spiro-MeOTAD HTM shows an impressive photovoltaic performance had the power conversion efficiency (PCE) of 11.54% when compared to the undoped TiO 2 photoanode PSSC. The results of this investigation indicate that the rare earth ion doping could be a promising method for producing effective ETL and enhanced performance PSSCs. • This work is mainly focused to increase the power conversion efficiency of photovoltaic devices using efficient photoanode structure, competence perovskite material with spiro-MeOTAD hole transport material. • The results showed in the present investigation, the device structure and the materials used in this study, significantly satisfied our focus of interest. [ABSTRACT FROM AUTHOR]

In this study, six small carbazole-based molecules are investigated for usage as hole transport materials (HTMs) in perovskite solar cells. Among these compounds, two molecules based on 9-(4-(thiophen-2-yl)phenyl)-9H-carbazole thiophene-phenyle and carbazole (M 1 and M 2) were already synthesized, and four new molecules are designed by substituting carbazole, in positions 3,6 and 2,7, with methoxyphenyl (P 1 and P 2) and dimethoxyphenylamine (E 1 and E 2). Theoretical methods used in the calculations included density functional theory and time-dependent density functional theory. FMOs of all under-probe molecules are well positioned to ensure accurate alignment and prevent charge recombination at the perovskite material interface. The molecules' absorbance in the area below 404 nm shows that HTMs cannot compete with perovskite materials in an inverted configuration of a device. Reorganization energies indicate that M 1 , P 1,2 and E 1,2 are more favourable to be HTM, while M 2 shows a favourable electron transfer; it can be used as an electron transfer material (ETM). The results demonstrate that hole-electron couples can easily separate for any under-exanimated molecules, simplifying hole transport and enhancing the short-circuit (J SC). Additionally, DMPA-based molecules (E 1,2) may display chemical instability because of their poor hardness and the local distribution of charge in electrostatic potential maps. [ABSTRACT FROM AUTHOR]

• Overview of CzDMPA based hole transporting materials (HTMs) for perovskite solar cells (PCSs) is discussed. • Classification of DMPA-containing carbazole based HTMs is given. • Research trends in synthetic pathways and structure-property relationship are reviewed. • Photovoltaic performance and stability in PCSs are summarized. Perovskite solar cells (PSC) based on metal-organic halide perovskites have emerged as one of the most promising photovoltaic technologies. Power conversion efficiency (PCE) has increased remarkably over the last few years from less than 10% up to certified efficiencies exceeding 23%. Selective interfacial layers play a critical role in charge extraction processes. In order to obtain high efficiencies, a hole transporting material (HTM) is required. Huge research efforts have been made to design efficient and low-cost materials. Carbazole-based HTMs are among the most promising new HTMs, in particular when they are substituted with dimethoxydiphenylamine (DMPA) units. This review gives an overview of the different classes of DMPA-containing carbazole-based HTMs and highlights the synthetic pathways, the structure-property relationship and the photovoltaic performances obtained in PSC devices. The relevance of structural variations and chemical doping processes is discussed with regard to efficiency and stability issues. [ABSTRACT FROM AUTHOR]

Abstract: This study reports design and synthesis of cone shaped hole transporting materials (HTM, i. e., H1 and H2). They are based on triphenylamine (TPA) and phenothiazine donors attached with two TPA moiety via electron rich π‐spacer (phenyl acrylonitrile). π‐spacers are proven to enhance the power conversion efficiency (PCE) of perovskite solar cells (PSCs) in the literature. Due to the electron withdrawing nature of the π‐spacer and the extended conjugation present in the HTMs proposed, a gradient for charge flow within the molecule is expected. This property is essential to transfer the electron from the HOMO of HTMs to the valence band of the perovskite via the arms of the HTMs. These HTMs do not show strong absorption in the visible region, exhibit high stokes shift and have their HOMO positioned above the perovskite's valence band. HTM layer of the PSCs were fabricated by a solution process method, at ambient conditions. A PCE of ∼1.9% at 1 sun condition was obtained, while under similar conditions the standard HTM (S‐OMeTAD) exhibited a PCE of 1.3%. [ABSTRACT FROM AUTHOR]

Hierarchical Temporal Memory is a new machine learning algorithm intended to mimic the working principle of the neocortex, part of the human brain, responsible for learning, classification, and making predictions. Although many works illustrate its effectiveness as a software algorithm, hardware design for HTM remains an open research problem. Hence, this work proposes an architecture for HTM Spatial Pooler and Temporal Memory with learning mechanism, which creates a single image for each class based on important and unimportant features of all images in the training set. In turn, the reduction in the number of templates within database reduces the memory requirements and increases the processing speed. Moreover, face recognition analysis indicates that for a large number of training images, the proposed design provides higher accuracy results (83.5%) compared to only Spatial Pooler design presented in the previous works. [ABSTRACT FROM AUTHOR]

We demonstrate for the first-time liquid exfoliated few layers of 2D Black phosphorus (BP) nanosheets as a hole transporting material (HTM) for perovskite based solar cells. The photoelectron spectroscopy in air (PESA) measurements confirm the low laying valence band level of BP nanosheets (−5.2 eV) favourable for hole injection from CH 3 NH 3 PbI 3 (MAPbI 3 ). Our results show that ∼25% improvement in power conversion efficiency (PCE) of η = 16.4% for BP nanosheets + Spiro-OMeTAD as an HTM as compared to spiro-OMeTAD (η = 13.1%). When BP nanosheets are exclusively utilised as an HTM, a PCE of η = 7.88% is noted, an improvement over the 4% PCE values observed for HTM free devices. Photoluminescence (PL) quenching of MAPbI 3 and impedance measurements further confirm the charge extraction ability of BP nanosheets. The structural and optical characterization of liquid exfoliated BP nanosheets is discussed in detail with the aid of transmission electron microscopy, Raman spectroscopy, absorption spectroscopy and photo-electron spectroscopy. [ABSTRACT FROM AUTHOR]

All-solid-state organic-inorganic halide perovskite solar cells (PSCs) have attracted wide attention due to the rapid progress of power conversion efficiency in recent years. Hole transport material (HTM) in PSCs plays the role of extracting and transporting photo-excited holes. Anisotropy of carrier mobility is one important property for semiconductors, however, which still remains unclear for the dominant HTM spiro-OMeTAD used in PSCs. Based on Density Functional Theory (DFT) and Marcus theory, we for the first time conducted investigations on the anisotropy of carrier mobility along representative crystal planes of spiro-OMeTAD by recombination energy λ and electronic coupling integral V . Results indicate that the holes and electrons show transport orientations consistency parallel to the (010), (101) and (111) crystal planes while inconsistency was found parallel to (100), (110), (011) and (001) crystal planes (with an angle ranged from 40° to 70° between the hole and electron transport directions). Our work embodies the theoretical significance of controllable and oriented fabrication of HTM in PSCs. [ABSTRACT FROM AUTHOR]

Quality of Experience (QoE) measurement in stereoscopic 3D is a challenging topic and existing standards such as ITU-R BT.500 may no longer be adequate for reliability and efficiency. Yet, objective measurement of QoE is not well researched for 3D images and videos. We present a new subjective assessment methodology providing better time-efficiency and more accurate scores at the same or even less number of assessors, using new objective metrics for QoE measurement of compressed multi-view video. Our research focus is twofold. First, the novel subjective testing methodology is developed, and QoE of different multi-view video compression technologies is evaluated. A time-efficient solution is proposed as a multiple stimuli plus simultaneous presentation extension of the conventional Double Stimulus Continuous Quality Scale (DSCQS) method. Second, objective quality metrics are proposed based on structural similarity and depth maps. Experiments are conducted on an auto-stereoscopic display while H.264/MPEG-4 Advanced Video Coding (AVC)- and High Efficiency Video Coding (HEVC)-based encoders are used for compression. The results demonstrate that the new methodology is superior to the DSCQS method in terms of both evaluation time and accuracy. Furthermore, high correlation is achieved with the new objective quality metrics. [ABSTRACT FROM AUTHOR]

One of the main obstacles to perovskite solar cells (PSCs) entering the market is the doping-induced degradation of expensive hole transport materials (HTMs), which results in poor device stability. Although lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and 4-tert-butylpyridine (4-tBp) as additives are commonly used in HTMs, they often lead to low device stability and reproducibility due to their hygroscopic and volatile nature. In this study, we incorporated the dilithium phthalocyanine (Li 2 Pc) molecule into the Spiro-OMeTAD precursor solution with Li-TFSI and 4-tBp to produce triple-cation PSCs with an n–i–p configuration operating with high efficiency and stability. The addition of the Li 2 Pc molecule not only improves the perovskite/Spiro-OMeTAD interface but also increases the π–π stacking in the thin-film phase according to the absorption and Raman results. Based on space-charge-limited current, photoluminescence, time-resolved photoluminescence and lifetime analysis measurements, charge transfer is improved with the Li 2 Pc molecule and charge recombination losses are reduced. As a result, the control device showed a power conversion efficiency (PCE) of 20.0% with J SC = 24.6 mA/cm2 and fill factor (FF) = 72.7%, whereas the Li 2 Pc-doped device exhibited an improved PCE of 20.6% with J SC = 25.0 mA/cm2 and FF = 73.6%. The addition of Li 2 Pc resulted in more stable and high-efficiency solar cells that maintained approximately 90% of the initial efficiency after 40 days. [Display omitted] • The addition of the Li 2 Pc molecule can increase the π–π stacking in the thin-film phase. • Li 2 Pc can effectively passivate the defects at the triple-cation perovskite/Spiro-OMeTAD interface. • The efficiency of triple-cation perovskite solar cell is increased from 20.0% to 20.6%. • The device with Li 2 Pc retained about 90% of the initial efficiency after 40 days compared to the control device. [ABSTRACT FROM AUTHOR]

Emerging development in perovskite sensitized solar cell have ushered in a transformative shift in the evolution of efficient and low-cost solar cell technologies. The improvement represents significant progress in the performance of sensitized solar cells since their breakthrough in 1991. Existing unexplored opportunities with these new developments depicts potential platform to achieve higher efficiency. Earlier development in solid state dye sensitized solar cells (DSSCs) has led to the incorporation of novel semiconductor nanocrystalline quantum dots (QDs) and perovskite as alternative sensitizer to improve device stability and enhance absorption coefficient. The attractiveness of perovskite CH3NH3PbI3 as sensitizer for solar cell incorporates its cost-effectiveness and light-harvesting capability which has shown consistent improvement in device performance in recent years. The incorporation of metal chalcogenides into solid-state dye sensitized solar cells showed significant improvement in power conversion efficiency (PCE) of 18.05%. With CH3NH3PbX3 (X=Cl, Br, or I) as an alternative to dye, device performance has shown to be promising although emerging challenges require a prioritized concern. In this review, recent exciting improvements in the performance of perovskite solar cells were discussed and the fundamental mechanisms incorporated into the structural evolution leading to PCE of 20.8%. In addition, prospects overriding present challenges were proposed for future work toward practical realization of highly- efficient solar cell upon optimization. [ABSTRACT FROM AUTHOR]

We have fabricated solution processed organic light-emitting devices (OLEDs) with various hole transporting materials (HTMs) on the plastic substrate. The device structure was ITO/HTM:Ir(2-phq)31wt%:FIrpic 5wt% (50 nm)/TAZ (50 nm)/LiF (0.5 nm)/Al (100 nm). 4,4′-bis(carbazol-9-yl)biphenyl (CBP), di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane (TAPC), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD), and poly(9-vinylcarbazole) (PVK) were used for HTM. Phosphorescent orange-red emitting Ir(2-phq)3and blue emitting FIrpic guest molecules were mixed with the HTMs and solvents. OLED with TAPC exhibited the maximum current efficiency of 17.4 cd/A at 0.42 mA/cm2. [ABSTRACT FROM AUTHOR]

Effective engineering of surface ligands in semiconductor nanocrystals can facilitate the electronic interaction between the individual nanocrystals, making them promising for low-cost optoelectronic applications. Here, the use of high purity Cu2ZnSnS4 (CZTS) nanocrystals as the photoactive layer and hole-transporting material is reported in low-temperature solution-processed solar cells. The high purity CZTS nanocrystals are prepared by engineering the surface ligands of CZTS nanocrystals, capped originally with the long-chain organic ligand oleylamine. After ligand removal, CZTS nanocrystals show substantial improvement in photoconductivity and mobility, displaying also an appreciable photoresponse in a simple heterojunction solar cell architecture. More notably, CZTS nanocrystals exhibit excellent hole-transporting properties as interface layer in perovskite solar cells, yielding power conversion efficiency (PCE) of 15.4% with excellent fill factor (FF) of 81%. These findings underscore the importance of removing undesired surface ligands in nanocrystalline optoelectronic devices, and demonstrate the great potential of CZTS nanocrystals as both active and passive material for the realization of low-cost efficient solar cells. [ABSTRACT FROM AUTHOR]

Due to their uncommon electronic properties, carbon-based nanomaterials have led to extensive research efforts in the field of photovoltaic energy conversion in the last two decades. Initially exploiting carbon nanotubes, carbon-based solar cells have now largely taken benefit from graphene and its various forms to demonstrate significant improvements in almost all device functions including charge generation, charge collection, and charge transport. More recently, hybrid metalorganic halide perovskites became one of the most promising materials for third generation solar cells, with efficiencies now competing with thin film technologies. While several issues remain to be addressed regarding device operation and stability, the incorporation of carbon-based nanostructures was rapidly proposed, and significant advances have been achieved so far. In this work, we review the recent progresses made in the specific field of graphene-based perovskite solar cells. We especially emphasize the relevance of the approach applied to hole and electron transport media (HTM and ETM), electrodes, as well as approaches aiming at improving the stability of the device. Tandem architectures based on graphene interlayers will also be discussed, illustrating the broad potentialities of graphene materials in the development of the perovskite-based photovoltaic technology. [ABSTRACT FROM AUTHOR]

An attempt has been made to fabricate methyl ammonium tin chloride (CHNHSnCl) perovskite-sensitized TiO nanostructure photoanode solar cell with hole transport material (HTM) spiro-MeOTAD and graphite-coated counter electrode (CE). The TiO nanoparticles (TNPs), TiO nanoleaves (TNLs), and TNLs with MgO core/shell photoanodes were prepared to fabricate perovskite-sensitized solar cells (PSSCs). The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The photovoltaic characteristics of the PSSCs, photocurrent density ( J ), open-circuit voltage ( V ), fill factor (FF), and power conversion efficiency (PCE) were determined under illumination of AM 1.5 G. Electrochemical impedance spectroscopy (EIS) analysis was carried out to study the charge transport and lifetime of charge carriers at the photoanode-sensitizer-electrolyte interface of the PSSCs. The PSSC made with CHNHSnCl perovskite-sensitized TNL-MgO core/shell photoanode and spiro-MeOTAD HTM shows an impressive photovoltaic performance, with J = 17.24 mA/cm, V = 800 mV, FF = 73 %, and PCE = 9.98 % under 100 mW/cm light intensity. The advent of such simple solution-processed mesoscopic heterojunction solar cells paves the way to realize low-cost and high-efficiency solar cells. By the aid of electrochemical impedance spectroscopy, it is revealed that the core/shell structure can increase an interfacial resistance of the photoanode-CHNHSnCl interface and retard an electron recombination process in the photoanode-sensitizer-HTM interface. [ABSTRACT FROM AUTHOR]

In this letter, we report on nanostructured NiO x with particle size ∼85 nm as an efficient hole transport material (HTM) for low temperature processed inverted planar perovskite solar cell (PSC) with power conversion efficiency of 15.64%. The homogenous NiO x HTM layer facilitated the growth of high quality CH 3 NH 3 PbI 3 absorber with large crystal grains and the resulting PSC showed stable photovoltaic performance under continuous illumination. [ABSTRACT FROM AUTHOR]

• Perovskite solar cells with device structure of FTO/TiO 2 /MAPbI 3 /GO + spiro-MeOTAD/Au has been developed. • GO + spiro-MeOTAD has been used as HTM. • PCE of 8.3% has been achieved using GO + spiro-MeOTAD as HTM. • The insertion of GO enhanced the stability of the perovskite solar cells. Herein, we reported the fabrication of perovskite solar cells (PSCs) with device architecture of FTO/TiO 2 /MAPbI 3 /GO + spiro-MeOTAD/Au. Graphene oxide (GO) was synthesized by Hummer's method which was further incorporated with spiro-MeOTAD to develop the stable PSCs. The fabricated PSCs device exhibited good efficiency of 8.3% using GO + spiro-MeOTAD/Au as hole-transport material (HTM) whereas control device (without GO) showed efficiency of 6.95%. PSCs device (with GO + spiro-MeOTAD) also exhibited good stability up to 168 h under controlled humidity (∼40–50%). [ABSTRACT FROM AUTHOR]

Background: Glaucoma is the largest cause of irreversible blindness affecting more than 60 million people globally. The disease is defined as a gradual loss of peripheral vision due to death of Retinal Ganglion Cells (RGC). The RGC death is largely influenced by the rate of aqueous humor production by ciliary processes and its passage through the trabecular meshwork (TM) in the anterior part of the eye. Primary open angle glaucoma (POAG), the most common subtype, is a genetically complex disease. Multiple genes and many loci have been reported to be involved in POAG but taken together they explain less than 10% of the patients from a genetic perspective warranting more studies in different world populations. The purpose of this study was to perform genome-wide search for common variants associated with POAG in an east-Indian population. Methods: The study recruited 746 POAG cases and 697 controls distributed into discovery and validation cohorts. In the discovery phase, genome-wide genotype data was generated on Illumina Infinium 660 W-Quad platform and the significant SNPs were genotyped using Illumina GGGT assay in the second phase. Logistic regression was used to test association in the discovery phase to adjust for population sub-structure and chi-square test was used for association analysis in validation phase. Publicly available expression dataset for trabecular meshwork was used to check for expression of the candidate gene under cyclic mechanical stress. Western blot and immunofluorescence experiments were performed in human TM cells and murine eye, respectively to check for expression of the candidate gene. Results: Meta-analysis of discovery and validation phase data revealed the association of rs7916852 in MPP7 gene (p = 5.7×10-7) with POAG. We have shown abundant expression of MPP7 in the HTM cells. Expression analysis shows that upon cyclic mechanical stress MPP7 was significantly down-regulated in HTM (Fold change: 2.6; p = 0.018). MPP7 protein expression was also found to be enriched in the ciliary processes of the murine eye. Conclusion: Using a genome-wide approach we have identified MPP7 as a novel candidate gene for POAG with evidence of its expression in relevant ocular tissues and dysregulation under mechanical stress possibly mimicking the disease scenario. [ABSTRACT FROM AUTHOR]

In this study, DFT calculations carried out using Carbazole-based HTMs substituted with dimethoxy phenylamine units (DMPA) in positions 2,3,6,7 and 9 are coupled with the experimental results drawn from the literature. The most important challenge for us is to establish a link between the optoelectronic and structural properties of molecules and their performance as HTMs. In this work, we find that the important structural effect is generated by the pyridinic nucleus. The substituents linked to the nitrogen atom of carbazole do not contribute to HOMO or LUMO in most of the studied HTMs. Hence, apart from the illustrated performances, parameters as the contribution of such substituents to being attached to the perovskite, or to the cohesion of the HTM's molecules contributing to the perovskite stability all prove decisive. The 2,7 substitution favors more stabilization of LUMOs when compared to 3,6 substitution, which leads to a narrow gap for 2,7 homologous. This makes these 2,7-substituted molecules good candidates as light absorbent in Organic Solar cells. The differences in the solar cell performances using these HTMs is mostly linked to the effect of these groups on their intermolecular interactions on one hand, and on the interfacial contact between HTMs and perovskite on the other hand. [ABSTRACT FROM AUTHOR]

This paper introduces a two-stage approach to the detection of people eating and/or drinking for the purposes of surveillance of daily life. With the sole use of wearable accelerometer sensor attached to somebody's (man or a woman) wrists, this two-stage approach consists of feature extraction followed by classification. At the first stage, based on the limb's three dimensional kinematics movement model and the Extended Kalman Filter (EKF), the realtime arm movement features described by Euler angles are extracted from the raw accelerometer measurement data. In the latter stage, the Hierarchical Temporal Memory (HTM) network is adopted to classify the extracted features of the eating/drinking activities based on the space and time varying property of the features, by making use of the powerful modelling capability of HTM network on dynamic signals which is varying with both space and time. The proposed approach is tested through the real eating and drinking activities using the three dimensional accelerometers. Experimental results show that the EKF and HTM based two-stage approach can perform the activity detection successfully with very high accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of imidazole-based Hole transfer Materials. • Excellent solution processability and stability suitable for efficient OLED. • HOMO levels for favourable hole injection as well as superior hole mobility. • The IMzB displayed current efficiency of 91.13 cd A−1 and EQE of 21.11%. • Highest current efficiency by solution processed green phosphorescent OLEDs. Organic small molecules have played a significant role in the field of organic light-emitting diodes (OLEDs) technology. Improving the stability of OLEDs continues to be a major task in organic electronics. To overcome this issue, it is essential to enhance the carrier injection into the emissive layer for better charge balance. Though OLEDs are highly desirable for the solution process, enabling simple and cost-effectively manufacturing to fabricate large-area devices, the development of hole-transporting materials (HTMs) still a considerable challenge. Herein the IMzN (1-(4-methoxyphenyl)-2-(4-nitrophenyl)-4,5-diphenyl-1H-imidazole) and IMzB (4-(1-(4-methoxyphenyl)-4,5-diphenyl-1H-imidazol-2-yl)benzoic acid) with excellent solution processability and stability suitable for efficient OLED devices using a simple and efficient microwave-assisted synthetic procedure. Thermogravimetric analysis of IMzN and IMzB suggested that the material be thermally stable up to 320–345 °C. No glass transition has occurred as confirmed by DSC indicating the amorphous nature of the materials, which is well supported by XRD analysis. Materials acquire the appropriate HOMO levels for favorable hole injection as well as superior hole mobility. As a result, both HTMs show better device performance than the commercially used TAPC. The IMzB as HTL shows remarkable current efficiency of 91.13 cd A-1 and EQE of 21.11%. This is the highest current efficiency reported using solution-processed green phosphorescent OLEDs. Devices with IMzB as HTL also exhibit relatively better stability under continuous stress. [ABSTRACT FROM AUTHOR]

Abstract: Recently, triphenylamine (TPA), 4,4′-bis(phenyl-m-tolylamino)biphenyl (TPD), 4,4′-bis(1-naphthylphenylamino)biphenyl (NPB) and their derivatives are widely used in the organic light-emitting diode (OLED) devices as a hole-transporting material (HTM) layer. We have optimized twenty different structures of HTM materials by using density functional theory (DFT), B3LYP/6-31G method. All these different structures contain mono-amine and diamine TPA derivatives. The energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) along with molecular orbitals for these HTMs are also determined. We have found that the central amine nitrogen atom and the phenyl ring, which is next to the central amine nitrogen atom, show significant contribution to the HOMO and LUMO, respectively. The sum of the calculated bond angles (α+β+γ) of the central amine nitrogen atom has been applied to describe the bonding and the energy difference for HOMO and LUMO in these TPA derivatives. Electronic structure calculations have been performed for these TPA derivatives. Again, the LCAO-MO patterns of HOMO and LUMO levels of these derivatives are used to investigate their electron density. A series of electron-transporting steps are predicted for these compounds employing these calculated results. [Copyright &y& Elsevier]

Abstract: Recently, triphenylamine (TPA) and its derivatives become widely used in the organic light emitting diode (OLED) devices as a hole transporting material (HTM). The calculated ionization potential (I p ) and reorganization energy for the hole transport (λ +) for a series of triphenylamine (TPA) derivatives are related to their Hammett parameters (σ and σ +) theoretically. In this study, the semiempirical AM1 method has been used to optimize thirty-three TPA derivatives. The electronic structures of these compounds in the neutral and the radical-cation states were obtained based on the optimized geometrical structure. The I p and λ + values were generated by means of the calculated heat of formation (or total energy) for both the neutral and the radical-cation states. In particular, the calculated I p ’s for these derivatives were consistent with experimental data. The substitution effect for the mono-substituted TPA derivatives is displayed in that the TPA derivatives with the electron-donating substituent have lower I p and those with electron-withdrawing substituent have higher I p , comparing to that of non-substituted TPA derivative. The substituent effect in di- and tri-substituted TPA derivatives is more pronounced than that of the mono-substituted TPA derivatives. According to the calculated results, the calculated I p shows an excellent agreement with the experimental oxidation potentials (E p/2) of these TPA derivatives. Furthermore, these calculated results can be employed to predict the electro-luminescence properties for new and improved HTM. [Copyright &y& Elsevier]

Summary Haematopoietic cell-specific transmembrane-4 (HTm4) is a four-transmembrane protein most closely related to CD20 and the beta subunit of the high affinity receptor for IgE (FcℇRIβ). To date, it has only been described in humans, where it is expressed in haematopoietic cells of both myeloid and lymphoid lineages. The function of HTm4 is unknown; however, as for CD20 and FcℇRI-β, it is likely to play a role in signal transduction as part of a multi-subunit cell surface receptor complex. In this study, we report the cDNA cloning and expression distribution of mouse HTm4. The deduced mouse HTm4 protein is of 213 amino acids, and contains four putative transmembrane domains. Mouse HTm4 shows 62% overall amino acid identity with human HTm4; the transmembrane regions are highly conserved between both species (75% identity), whereas the N- and C-terminal and inter-transmembrane loop regions are more divergent (52%). Interestingly, the N-terminal domain of mouse HTm4 is predicted to be 23 amino acids shorter, and the C-terminal domain 23 amino acids longer, than that of human HTm4. Northern blot and reverse transcriptase (RT)-PCR analysis suggest that mouse HTm4 mRNA is expressed at low levels only in spleen, bone marrow and peripheral blood leucocytes. This is the first report of the cloning of HTm4 from a species other than human, and provides important sequence information towards the understanding of the function of this poorly characterized four-transmembrane molecule. [ABSTRACT FROM AUTHOR]

Planar perovskite solar cells were fabricated on F-doped SnO2 (FTO) coated glass substrates, with 4,4'-((1E,1'E)-((1,2,4-thiadiazole-3,5-diyl)bis(azaneylylidene))bis(methaneylylidene))bis(N,N-di-p-tolylaniline) (bTAThDaz) as hole transport material. This imine was synthesized in one step reaction, starting from commercially available and relatively inexpensive reagents. Electrochemical, optical, electrical, thermal and structural studies including thermal images and current-voltage measurements of the full solar cell devices characterize the imine in details. HOMO-LUMO of bTAThDaz were investigated by cyclic voltammetry (CV) and energy-resolved electrochemical impedance spectroscopy (ER-EIS) and were found at −5.19 eV and −2.52 eV (CV) and at −5.5 eV and −2.3 eV (ER-EIS). The imine exhibited 5% weight loss at 156 °C. The electrical behavior and photovoltaic performance of the perovskite solar cell was examined for FTO/TiO2/perovskite/bTAThDaz/Ag device architecture. Constructed devices exhibited good time and air stability together with quite small effect of hysteresis. The observed solar conversion efficiency was 14.4%. [ABSTRACT FROM AUTHOR]