Search results for "photovoltaic"
showing 10 items of 646 documents
Charge Transport Properties in CZT Detectors Grown by the Vertical Bridgman Technique
2010
Great efforts are being presently devoted to the development of CdTe and CdZnTe detectors for a large variety of applications, such as medical, industrial, and space research. We present the spectroscopic properties of some CZT crystals grown by the standard vertical Bridgman method and by the boron oxide encapsulated vertical Bridgman method, which has been recently implemented at IMEM-CNR (Parma, Italy). By this technique the crystal is grown in an open quartz crucible fully encapsulated by a thin layer of liquid boron oxide. This method prevents contact between the crystal and the crucible thereby allowing larger single grains with a lower dislocation density to be obtained. Several mono…
Polarization backward-wave four-wave mixing in BaTiO_3:Fe using the photovoltaic effect
1997
We report the first study to our knowledge of polarization backward-wave four-wave mixing in a BaTiO3:Fe crystal and compare the results of our measurements with the calculations performed within the model of photovoltaic charge transport. Two identically polarized pump waves and one orthogonally polarized signal wave are sent to a sample in a plane normal to the crystal’s C axis; a phase-conjugate wave with polarization identical to that of the signal wave is generated. With a 2-mm-thick sample a phase-conjugate reflectivity Rpc≈0.01 is reached; for a 1-cm-thick sample, amplified reflection should be possible.
Vacuum-Deposited Microcavity Perovskite Photovoltaic Devices
2021
The interaction between semiconductor materials and electromagnetic fields resonating in microcavities or the light-matter coupling is of both fundamental and practical significance for improving the performance of various photonic technologies. The demonstration of light-matter coupling effects in the emerging perovskite-based optoelectronic devices via optical pumping and electrical readout (e.g., photovoltaics) and vice versa (e.g., light-emitting diodes), however, is still scarce. Here, we demonstrate the microcavity formation in vacuum-deposited methylammonium lead iodide (CH3NH3PbI3, MAPI) p-i-n photovoltaic devices fabricated between two reflecting silver electrodes. We tune the posi…
Photocycle of Excitons in Nitrogen-Rich Carbon Nanodots: Implications for Photocatalysis and Photovoltaics
2020
Nitrogen-rich carbon nanodots have emerged as promising nanomaterials for a wide range of applications where a highly emissive and photoactive material with low toxicity and cost-effectiveness is required. One of their hallmarks is indeed a bright, tunable fluorescence of excitonic nature. Disentangling the origin of their optical absorption and fluorescence properties and uncovering relaxation channels and interactions with solvents are some of the most debated issues in the field. Uncovering these aspects is essential for targeted applications, especially in the fields of photocatalysis but also photovoltaics and optoelectronics. Here, we present dedicated transient absorption measurement…
Local Bonding Influence on the Band Edge and Band Gap Formation in Quaternary Chalcopyrites
2017
Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu2ZnGeS4-x Se x , the anion bond alteration parameter changes, showing larger bond lengths for metal-selenium than for metal-sulfur bonds. The changing bonding interaction directly influences the valence and conduction band edges, which result from antibonding Cu-anion and Ge-anion interactions, respectively. The knowledge of the underlyi…
ZnS Ultrathin interfacial layers for optimizing carrier management in Sb2S3-based photovoltaics
2021
Antimony chalcogenides represent a family of materials of low toxicity and relative abundance, with a high potential for future sustainable solar energy conversion technology. However, solar cells based on antimony chalcogenides present open-circuit voltage losses that limit their efficiencies. These losses are attributed to several recombination mechanisms, with interfacial recombination being considered as one of the dominant processes. In this work, we exploit atomic layer deposition (ALD) to grow a series of ultrathin ZnS interfacial layers at the TiO2/Sb2S3 interface to mitigate interfacial recombination and to increase the carrier lifetime. ALD allows for very accurate control over th…
Role of TiO2 in Highly Efficient Solar Cells
2021
Titanium dioxide (TiO2) is a naturally occurring oxide of titanium. It has a wide range of applications. It has three metastable phases, which can be synthesized easily by chemical routes. Usage of TiO2 in thin-film solar cells has gained much attention in increasing the performance of the cell. The objectives are to harvest the freely available earth’s energy and to gain expertise in yielding a maximum conversion efficiency. Various strategies are employed to face the challenges in improving the efficiency of solar cells. This study provides a broad view of the usage of different forms of TiO2 layers, like nanochannel, porous, nanotubes, and mesoporous layers, in enhancing electron injecti…
Optimal Sizing and Siting of Distributed Energy Resources Considering Public and Private Incentive Policies
2008
The present work presents the formulation and solution approach for the problem of optimal sizing and siting of distributed energy resources based on Photovoltaic, PV, technology. The considered system is an isolated grid (small island) and the parts involved are the utility and the customers. As it happens in islands, the same utility generates and delivers energy to customers, for this reason, the installation of dispersed generation units is beneficial for reducing power losses, regularizing the voltage profile, but also for increasing the profit. The problem is solved by means of the Non dominated sorting Genetic Algorithm II, NSGA-II, identifying the optimal size and location of PV sys…
Dynamic programming and Munkres algorithm for optimal photovoltaic arrays reconfiguration
2015
Abstract In this paper, an original formulation of the control problem for optimal PV array reconfiguration, following a Total Cross Tied layout, is proposed. The formulation follows the well-known subset sum problem, which is a special case of the knapsack problem. The reconfiguration is a measure devoted to mitigate the mismatch effect and maximize the output power of small photovoltaic plants under non-homogeneous working conditions. Therefore, reconfiguration means changing the connections of the solar panels adaptively by a dynamic switching matrix. The control system implements an easy dynamic programming algorithm to change the switches layout. The use of the Munkres assignment metho…
Parked electric car's cabin heat management using photovoltaic powered ventilation system
2019
Abstract This paper explores the use of electric car roof mounted photovoltaic (PV) powered ventilation for cabin heat management/ventilation. A fully-functional Renault Zoe electric car has been used for performance evaluation of parked electric car ventilation directly powered by PV. This work has been part of a research project of testing electric cars in the urban environment and it has been conducted at the Edinburgh Napier University’s Transport Research Institute. In this work, parked electric car ventilation has been reported, when roof-mounted PV modules were used to operate DC powered fans for ventilation. It has been found that the DC motor-fan selection for removing the hot air …