United States

Conversion efficiencies of photovoltaic cells have been measured based on a calorimetric method or electrical substitution method. To automatize the electrical substitution, a constant temperature control is adopted. For a silicon photodiode as a photovoltaic cell, its internal conversion efficiency and internal spectral responsivity have been directly evaluated by using a Peltier device as a temperature difference sensor and use a thermistor as a heater. Its external spectral responsivity obtained by the calorimetric method agrees to an optically calibrated value within 11%.

AIP Publishing Horizons - Energy Storage and Conversion

Direct Measurement for Internal Conversion Efficiency of Photovoltaic Cells Based on Calorimetric Method

electrical substitution

calorimetric

photovoltaic cell

conversion efficiency

photodiode

## Dr. Nishikant (Nish) Sonwalkar: Academician, Scientist, Musician

![](https://assets.underline.io/uploads/markdown_image/1/image/0f9b63a0b3deba4a355d98e2c87af68a.png)

Dr. Sonwalkar is regarded as a leading expert in the application of computers in education. He has extensive research and development experience in hypermedia authoring, mobile learning, adaptive learning, and brain-based synaptic learning, advanced scientific visualization, database management systems, and computer simulation.

After receiving doctoral degree from MIT in the area of Molecular Dynamics of Nano-interfaces, he joined MIT as faculty in Mechanical Engineering, but his passion for technology enabled education led him become the founding director of Hypermedia Teaching Facility (Hypermedia Lab) at MIT and later he was appointed as the Principal Educational Architect of MIT.

<iframe width="560" height="315" src="https://www.youtube.com/embed/dgGdFmr9kgs" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

NISH 2021

poster

Energy conversion and storage is a critical part of modern society. Applications continue to develop at a fast pace, from the development of new generation battery materials, to environmental sensors, catalytic materials for sustainable energy and solar cells and photodetectors. This conference will cover the latest advances in energy related fields and debate the needs and priorities currently existing or emerging in this field over the next few decades.

Conference Topics:

* Batteries and supercapacitors
* Catalytic materials and water splitting
* Light emitting materials and devices
* Solar cells and photodetectors
* Thermoelectric materials
* Sensing and environmental monitoring systems


If you have any questions, please visit the [Help Desk](https://underline.io/events/155/help-desk). 

To access the AIPP Energy Storage and Conversion conference, [please remember to register.  ](https://services.aip.org/AIPPHorizons/?confID=3351205)

Energy conversion and storage is a critical part of modern society. Applications continue to develop at a fast pace, from the development of new generation battery materials, to environmental sensors, catalytic materials for sustainable energy and solar cells and photodetectors. This conference will cover the latest advances in energy related fields and debate the needs and priorities currently existing or emerging in this field over the next few decades.

X-ray Absorption Spectroscopy (XAS) is being used for capturing the reaction mechanisms at the molecular level via the determination of local electronic configurations inside the Li-S batteries. In this work, a comprehensive investigation of the S K-edge X-ray Absorption Near-Edge Structure (XANES) of a series of stoichiometric lithium polysulfide solids1,2,3 was performed assuming that such polysulfides are being formed during the battery cycling process. The results based on density functional theory show that the pre-edge peak in the S K-edge XANES spectra does not occur in the solid phase in contrast to the case of polysulfide molecules where the pre-edge peak constitutes a unique signature in liquid electrolytes. A general redshift in XANES S K-edge peak is found when the Li-vacancy is introduced for these lithium polysulfide solids. Furthermore, the first peak positions of the S K-edge XANES spectra of the solid lithium polysulfides appear within a small range (2471-2473 eV) overlapping with the α-S8 bulk’s white line (~ 2472 eV). The results, therefore, suggest the use of additional characterization methods might be necessary in accurately identifying the elusive solid phase lithium polysulfides in Li-S battery instead of relying only on the S K-edge XANES spectra.

First-Principles Study of XANES Study on Lithium Polysulfide Solids

We have focused on the fabrication of low-cost Cu-based large-area perovskite solar cells and their stability studies in our present work. The large area devices with the structure FTO/c-TiO2/mTiO2/MAPbI3/Spiro-OMeTAD/Cu were fabricated by the two-step spin coating method. The X-ray diffraction analysis confirmed the formation of a tetragonal phase of the perovskite material. The small area device (0.25 cm2) showed a photoconversion efficiency (PCE) of 8.91%, whereas the scaled-up device with an area of 2.5 cm2 showed a PCE of 4.36%. Eight such large area devices were fabricated.The statistical distribution of fabricated devices showed an average value of 4.06 %, with a standard deviation of 0.31%. The stability of the fabricated devices under ambient environment conditions for two weeks showed that the significant changes in the device efficiency occurred due to a decrease in photocurrent. It happened primarily because of the active layer degradation, resulting in a loss of light absorption.

Fabrication of Cu Electrode Based Large-Area Perovskite Solar Cells and Their Stability Analysis

Over past half-century, the cardiac pacing technology always maintains one basic system paradigm, particularly the power supply and the leads, which brings out many pacemaker-related complications. Implantable piezoelectric energy harvesting has been demonstrated as one of the promising batteryless pacing technologies. A heart-worn pacemaker strategy, which allows batteryless powering and leadless pacing, has been firstly presented by our research group recently. The key challenge is to obtain sufficient power supply in vivo. Our buckled piezoelectric energy harvesting strategy performs great potential. The d31 and d33 coupled mode has been presented for this conversion process. The behavior of d31 and d33 coupled piezoelectric dynamics is discussed.

Mechanism on Buckled Piezoelectric Energy Harvesting for Batteryless Heart-worn Pacemaker

Hydrogen has considerable potential as an alternative fuel because it is carbon-free, facilitates the use of more efficient power generation systems, and can reduce carbon oxides to chemical fuels chemically. Solar-to-chemical energy conversion of water to H2 is especially attractive given the abundance of water and the free energy available in sunlight. While TiO2 absorbs little of the solar spectrum, doping may redshift the TiO2 absorption spectrum into the visible. In the case of noble metals, if the size is reduced below its electron mean path, it induces the property of visible and near UV light absorption1. The incorporation of gold nanostructures to modify the surfaces leads to a remarkable improvement in photonic activity owing to the formation of Schottky barriers that prevent the recombination of photogenerated electron-hole pairs. Gold nanoclusters (Au NCs) are smaller in size than Au NPs and are used to modify surface properties. In contrast to nanoparticles, it is not the crystal structure but the geometric fluxionality and the size dependence of the electronic structure important for surface modification by clusters. For this reason, the number of atoms forming an Au NC strongly influences the properties of NCs modified surfaces. The catalytic properties of cluster-modified surfaces change with the size of Au NCs, and the size of the NCs needs to be preserved to retain specific surface properties. Agglomeration of NCs leads to an increase in NC size, eventually forming NPs, and should be avoided; otherwise, the agglomeration strongly affects the photocatalytic properties of the catalyst2. Application of mesoporous TiO2 with remarkable surface defects, high surface area, and extensive 3D pore network can be beneficial to prevent agglomeration of gold clusters after post heat treatment. Also, to have stronger interaction between Au NCs and semiconductor surface leading to decreased agglomeration and increasing the loading of the Au NCs, the functionalizing reagent is used to make a system with a high number of active sites to obtain highly active photocatalytic systems.

Highly Efficient Binding Au9 Clusters to Chemically S-Modified Mesoporous TiO2 Films

Flexible thermoelectric aerogel composites are synthesized through solution processing, and the
corresponding behavior can be understood through pressure-dependent percolation theory.

Thermoelectric Composite Aerogels for Scalable Energy Harvesting Threads

Metal halide perovskites have been recently proposed as hopeful materials for energy storage applications.1,2 Despite the quite important electrochemical characteristics of these materials, all the perovskite-based anodes are synthesized at high temperatures (90–150 °C) and with reaction durations of the order of tens of hours. In this work, we present perovskite materials synthesized with room temperature, simple and fast approaches for high-performance and stable electrodes for Li-air batteries. Hexagonally-shaped nanocrystals capped with ligands3 and ligand free microcubes4 synthesized with re-precipitation based protocols will be compared according to their storage capacity and stability. Specifically, it is shown that the electrodes incorporating the ligand free microcubes present unprecedented stability complemented with high specific capacity. These could be attributed to the high crystal quality of the materials and thus enhanced electrical conductivity, even under operation with an aqueous electrolyte. The large interfacial area between the perovskite material and the electrolyte along with the increase of the active sites on the exposed microcubes facets favor the Li ion intercalation. In addition, the absence of capping ligands contributes further to the enlargement of contact area, and facilitates the ion penetration compared to ligand capped nanocrystals. The good crystallinity of the microcubes enhances the Li-ion intercalation and the electron transportation. The microcubes performance is the best among all the anodes utilizing metal halide perovskite nanostructures, reported to date.

Metal halide perovskites for low-cost and safe Li-air batteries

Ligand-free CsPbBr3 rounded cubes (RC) with average size of 3 μm have been prepared via a facile solution process under ambient conditions. The ability to grow directly the microcrystals onto electrodes provides a simple and low-cost method for the fabrication of high-performance perovskite-sensing elements, operating at room temperature without external stimuli (heating or UV irradiation). We show that the ambient synthesis conditions results in the growth of imperfect, rounded cube-shaped crystals. It is revealed that this shape favored the gas sensing process and as a consequence the RC-based sensors exhibited superior sensing performance compared to regular CsPbBr3 cubes (capable to detect 187 ppb ozone concentration) synthesized in inert atmosphere.1 The RC detect 4 ppb of ozone concentration with sensitivity of 13% at room temperature. Their response and recovery times at this low concentration, lays at 74 s and 15 s, respectively. RC-based sensor show also remarkable stability over consecutive cycles and after 3 months its storage in ambient conditions, without obvious alterations in morphology and crystal structure. At the same time, RCs proved to be superior hydrogen sensors, exhibiting capability to detect 1 ppm of hydrogen concentration. Both gas sensors developed, exhibit the lowest reported gas detection limits at room temperature compared to state-of-the art semiconductor materials, providing new opportunities in gas sensing applications (Figure 1). The enhanced sensitivity as well as the ease of the preparation method makes CsPbBr3 RCs as a good candidate for the detection of other types of gases as well.

CsPbBr3 perovskite microcrystals and their capability to detect ultra-low ozone and hydrogen concentrations

Designing electrocatalytically active cathode materials for Sodium Sulfur batteries: a DFT study

(p×n)-type transverse thermoelectrics were proposed as a potential superior thermoelectric material for Peltier cooling at cryogenic temperature and integrated thermoelectric devices. In transverse thermoelectric materials, highly anisotropic ambipolar conduction leads to the opportunity to achieve off-diagonal Seebeck coefficient through proper orientation, which generates a voltage drop perpendicular to the temperature gradient. Some anisotropic thermoelectric materials are found to have ambipolar Seebeck effect, with a negative Seebeck coefficient along one direction and positive orthogonal Seebeck, hence the name (p×n)-type. However, such experiments only measured Seebeck coefficients along particular crystal axes, which is insufficient to map the full Seebeck tensor. Also, different samples are often used for different orientations so sample inhomogeneity makes such measurements less reliable. Here, we report results for an all-in-one measurement set-up for measuring the full Seebeck tensor on a single sample with custom-made apparatus. The details of the fabrication, sources of error, and typical measurements are described. Measurements on pre-characterized isotropic thermoelectric material PbTe are reported. The obtained diagonal Seebeck coefficients agree with results from standard measurement methods to within 10%, and the errors introduced in the 6 off-diagonal terms are less than 5% of the diagonal values. Anisotropic van der Pauw measurements can also be integrated into the apparatus to measure the full anisotropic resistivity tensor on the same sample.

Full Experimental Seebeck Tensor Characterization for (p × n)-Type Transverse Thermoelectrics

This study explores the sustainable feasibility of kitchen waste extract as a photosensitizer for Dye Sensitized Solar Cell (DSSC). The dye was extracted from Onion peels by conventional soaking method. The dye extract was characterized by Thin Layer Chromatography (TLC) and UV-Visible spectroscopy at room temperature. These characterizations technique indicates anthocyanin pigment in the extracted dye from the Onion peel. The maximum absorbance was found at wavelength 533nm in the UV-Visible spectra with direct band gap (Eg) at 2.14eV from Tauc plot and Eg = 2.2eV from numerical derivative dA/dE as well. This crude extract was used as a photosensitizer in DSSC. This DSSC was characterized by using Keithley 2450 Source Meter in presence of tungsten bulb illumination. The key performance parameters were also computed i.e., short circuit current (ISC = 2.42 𝜇𝐴), open-circuit voltage (Voc = 0.51 mV), fill factor (FF = 0.27) and efficiency ( 𝜂 = 3.8〖×10〗^(−5) %) under tungsten bulb illumination without giving any pre-treatment to the components of DSSC. 



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First-Principles Study of XANES Study on Lithium Polysulfide Solids

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