Highly efficient planar perovskite solar cells through band alignment engineering

The simplification of perovskite solar cells (PSCs), by replacing the mesoporous electron selective layer (ESL) with a planar one, is advantageous for large-scale manufacturing. PSCs with a planar TiO2 ESL have been demonstrated, but these exhibit unstabilized power conversion efficiencies (PCEs). Herein we show that planar PSCs using TiO2 are inherently limited due to conduction band misalignment and demonstrate, with a variety of characterization techniques, for the first time that SnO2 achieves a barrier-free energetic configuration, obtaining almost hysteresis-free PCEs of over 18% with record high voltages of up to 1.19 V

ATM QoS prediction using neural-networks

Future broadband integrated services digital networks (B-ISDN) will be based on asynchronous transfer mode (ATM) technology. ATM traffic management and congestion control is needed to guarantee the quality of service (QoS) parameters. Artificial neural networks (ANN) have several properties that are valuable when implementing ATM traffic control. A neural network based QoS estimation is presented to enhance the performance of ATM management so that service providers offer better services to their clients. A divide and conquer approach is proposed, which can be used for efficient classification. This architecture can be trained faster than conventional neural network architecture and it can classify the data more efficiently. Multilayer perceptron (MLP) and radial basis function networks (RBFN) are also trained for QoS estimation and their performances are compared. Results indicate that the proposed architecture outperforms MLP and RBF network

ATM QoS prediction using neural-networks

Future broadband integrated services digital networks (B-ISDN) will be based on asynchronous transfer mode (ATM) technology. ATM traffic management and congestion control is needed to guarantee the quality of service (QoS) parameters. Artificial neural networks (ANN) have several properties that are valuable when implementing ATM traffic control. A neural network based QoS estimation is presented to enhance the performance of ATM management so that service providers offer better services to their clients. A divide and conquer approach is proposed, which can be used for efficient classification. This architecture can be trained faster than conventional neural network architecture and it can classify the data more efficiently. Multilayer perceptron (MLP) and radial basis function networks (RBFN) are also trained for QoS estimation and their performances are compared. Results indicate that the proposed architecture outperforms MLP and RBF network

Non-aggregated Zn(ii)octa(2,6-diphenylphenoxy) phthalocyanine as a hole transporting material for efficient perovskite solar cells

A non-aggregated Zn(ii)octa(2,6-diphenylphenoxy) phthalocyanine (coded as TT80) has been used as a hole-transporting material for perovskite solar cells. The cells were fabricated under three different configurations by changing the uptake solvent (chlorobenzene or toluene) and incorporating additives (bis(trifluoromethane) sulfonimide lithium salt (LiTFSI) and 4-tert-butylpyridine (TBP). A power conversion efficiency of 6.7% (AM1.5G standard conditions) was achieved for the best cell under optimized configurationWe are grateful for the financial support of the MEC, Spain (CTQ2014-52869/BQU), Comunidad de Madrid, Spain (FOTOCARBON, S2013/MIT-2841), and the European Union within the FP7-ENERGY-2012-1, nr. 309194-2, GLOBALSOL project. M. K. N. thanks the European Union for funding within the Seventh Framework Program [FP7/2007–2013] under the grant agreement no. 604032 of the MESO projec

CdSe quantum dot (QD) and molecular dye hybrid sensitizers for TiO2 mesoporous solar cells: working together with a common hole carrier of cobalt complexes

Redox couples based on cobalt complexes were found to be effective in regenerating both inorganic CdSe quantum dot-and organic dye-sensitizers. The hybrid sensitizer composed of CdSe QD and ruthenium sensitizer (Z907Na) dye showed a maximum power conversion efficiency of 4.76% on using cobalt(o-phen)(3)(2+/3+) as a common redox mediator.close202

A distributed framework for relaying stereo vision for telerobotics

Stereo vision is one critical tool in minimally invasive surgery (MIS) for enhancing perception of depth of organs which greatly improves the operation efficiency. Augmented stereo views results from superimposing 3D anatomical models with real organ views. A reliable distributed framework for relaying stereoscopic visual feedbacks between a telerobotic server and a client station is proposed. The distributed components are based on DirectX, Visual C#, and Window sockets. We used a multi-threaded execution to promote concurrency in grabbing, transmitting, receiving, processing, and displaying image data using head-mounted display (HMD) technology. The client station provides components that support augmented reality (AR), i.e. superimposing animated graphic model with real views from the operating site. Design and performance issues of proposed multi-threaded execution for streaming of stereo data in a distributed and modular framework is presented

All-inorganic core-shell silica-titania mesoporous colloidal nanoparticles showing orthogonal functionality

Colloidal mesoporous silica (CMS) nanoparticles with a thin titania-enriched outer shell showing a spatially resolved functionality were synthesized by a delayed co-condensation approach. The titaniashell can serve as a selective nucleation site for the growth of nanocrystalline anatase clusters. These fully inorganic pure silica-core titania-enriched shell mesoporous nanoparticles show orthogonal functionality, demonstrated through the selective adsorption of a carboxylate-containing ruthenium N3-dye. UV-Vis and fluorescence spectroscopy indicate the strong interaction of the N3-dye with the titania-phase at the outer shell of the CMS nanoparticles. In particular, this interaction and thus the selective functionalization are greatly enhanced when anatase nanocrystallites are nucleated at the titania-enriched shell surface

Impact of monovalent cation halide additives on the structural and optoelectronic properties of CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> perovskite

The influence of monovalent cation halide additives on the optical, excitonic, and electrical properties of CH$_{3}$NH$_{3}$PbI$_{3}$ perovskite is reported. Monovalent cation halide with similar ionic radii to Pb$^{2+}$, including Cu$^{+}$, Na$^{+}$, and Ag$^{+}$, have been added to explore the possibility of doping. Significant reduction of sub-bandgap optical absorption and lower energetic disorder along with a shift in the Fermi level of the perovskite in the presence of these cations has been observed. The bulk hole mobility of the additive-based perovskites as estimated using the space charge limited current method exhibits an increase of up to an order of magnitude compared to the pristine perovskites with a significant decrease in the activation energy. Consequentially, enhancement in the photovoltaic parameters of additive-based solar cells is achieved. An increase in open circuit voltage for AgI (≈1.02 vs 0.95 V for the pristine) and photocurrent density for NaI- and CuBr-based solar cells (≈23 vs 21 mA cm$^{−2}$ for the pristine) has been observed. This enhanced photovoltaic performance can be attributed to the formation of uniform and continuous perovskite film, better conversion, and loading of perovskite, as well as the enhancement in the bulk charge transport along with a minimization of disorder, pointing towards possible surface passivation.M.A.J. thanks Nyak Technology Limited for a PhD scholarship. M.I.D., S.M.Z., and M.G. thank the King Abdulaziz City for Science and Technology (KACST) and Swiss National Science Foundation (SNSF) for financial support. N.A. gratefully acknowledges financial support from the Swiss confederation under Swiss Government Scholarship program. The authors would like to thank Dr. Pierre Mettraux in Molecular and Hybrid Materials Characterization Center, EPFL for carrying out XPS measurements. A.S. gratefully acknowledges financial support from the Indo-UK APEX project. S.P.S. acknowledges Royal Scociety London for the Newton Fellowship. R.H.F, M.A.J., and A.S. would like to acknowledge the support from EPSRC.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/aenm.20150247

A distributed framework for relaying stereo vision for telerobotics

Stereo vision is one critical tool in minimally invasive surgery (MIS) for enhancing perception of depth of organs which greatly improves the operation efficiency. Augmented stereo views results from superimposing 3D anatomical models with real organ views. A reliable distributed framework for relaying stereoscopic visual feedbacks between a telerobotic server and a client station is proposed. The distributed components are based on DirectX, Visual C#, and Window sockets. We used a multi-threaded execution to promote concurrency in grabbing, transmitting, receiving, processing, and displaying image data using head-mounted display (HMD) technology. The client station provides components that support augmented reality (AR), i.e. superimposing animated graphic model with real views from the operating site. Design and performance issues of proposed multi-threaded execution for streaming of stereo data in a distributed and modular framework is presented

Influence of Charge Transport Layers on Open Circuit Voltage and Hysteresis in Perovskite Solar Cells

Perovskite materials have experienced an impressive improvement in photovoltaic performance due to their unique combination of optoelectronic properties. Their remarkable progression, facilitated by the use of different device architectures, compositional engineering, and processing methodologies, contrasts with the lack of understanding of the materials properties and interface phenomena. Here we directly target the interplay between the charge-transporting layers (CTLs) and open-circuit potential (VOC) in the operation mechanism of the state-of-the-art CH3NH3PbI3 solar cells. Our results suggest that the VOC is controlled by the splitting of quasi-Fermi levels and recombination inside the perovskite, rather than being governed by any internal electric field established by the difference in the CTL work functions. In addition, we provide novel insights into the hysteretic origin in perovskite solar cells, identifying the nature of the contacts as a critical factor in defining the charge accumulation at its interface, leading to either ionic, electronic, or mixed ionic-electronic accumulation