Photoluminescence of nanocrystals embedded in oxide matrices

Estrada, Cesar A.; Gonzalez, J. A.; Kunold, A.; Reyes‐Esqueda, Jorge‐Alejandro; Pereyra, Pedro

doi:10.1002/pssc.200673264

Cited by 2 publications

(4 citation statements)

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“…All of them are just capable of simulating a single set of PV generator-frequency converter-motor pump, include default settings for inexperienced users, and use simple sizing methods such as the so-called "peak month" method. There are also other tools for the design and sizing of irrigation networks, such as Hydrocalc [25] or GESTAR [26,27], and tools for irrigation requirements depending on the crop needs, such as CROPWAT [28].…”

Section: Introductionmentioning

confidence: 99%

Modeling and Simulation of Multipumping Photovoltaic Irrigation Systems

2022

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The growing market of large-power photovoltaic irrigation systems (PVISs)—made of systems with different and several motor pumps working in parallel—needs simulation tools capable to estimate their energy and water productivity. The objective of this paper is to present the simulation models developed for parallel multipump PVISs fed by a single PV generator. These models seek to maximize the instantaneous water flow rate according to the available PV power and were developed for the typical configurations of large-power irrigation facilities. The models present some advantages when compared with the current state of the art (in which a single motor pump connected to a 1/N fraction of the PV generator is simulated and the result is multiplied by N): in the case of negligible hydraulic friction losses, the use of the multipump model shows gains with respect to the state of the art; in the case of appreciable friction losses, the current state of the art overestimates the productivity of the systems. Then, the ability of these models to compare different multipump designs is shown: two groups of pumps working at variable frequencies show better performance than a group working at a variable frequency and a group at a nominal frequency—an 8% increase in the water pumped is seen.

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Section: Introductionmentioning

confidence: 99%

Modeling and Simulation of Multipumping Photovoltaic Irrigation Systems

2022

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“…[1][2][3][4][5][6] As the film thickness decreases, the surface to volume ratio increases and affects the complexity of the surface morphology. Thus, amorphous germanium with dangling bonds and grain boundaries as well as nanocrystalline and microcrystalline grains of random orientation are known to arise.…”

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confidence: 99%

“…Germanium thin films deposited on various substrates are known to give rise to unusual and interesting properties that are important from the point of view of both optoelectronic and microelectronic applications. [1][2][3][4][5][6] As the film thickness decreases, the surface to volume ratio increases and affects the complexity of the surface morphology. Thus, amorphous germanium with dangling bonds and grain boundaries as well as nanocrystalline and microcrystalline grains of random orientation are known to arise.…”

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confidence: 99%

“…Thus, amorphous germanium with dangling bonds and grain boundaries as well as nanocrystalline and microcrystalline grains of random orientation are known to arise. 1,7 The sizes of the particles and the surface structures are critical for thin film properties such as photoluminescence ͑PL͒, 1,2,6 electrical resistance, 1 etc. It has been shown that the bandgap of germanium nanocrystalline thin films increases when the film thickness decreases from 200 to 5 nm.…”

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Structural, Vibrational, and Optical Characterization of Anodically Electroplated Germanium Thin Films

Chandrasekharan

Sevov

2010

J. Electrochem. Soc.

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Germanium thin films were anodically electrodeposited from ethylenediamine solutions of K 4 Ge 9 which contain the well known Ge 9 4− deltahedral Zintl ions. The anodes were p-doped Si͑100͒ wafers or ITO-covered glass slides. The films were studied for their optical and structural properties by Raman spectroscopy, TEM, and luminescence measurements. The Raman spectra of the films show peaks shifted to lower frequencies compared to the same peaks in bulk germanium and indicate nanocrystalline structure for the films. This is further corroborated by the TEM observations. Laser-induced crystallization at selected areas of the films results in significant growth of the nanocrystals. The films exhibit photoluminescence in the visible light range. This has been attributed to a combination of nanocrystallinity and surface defects. Overall, the optical and structural properties of the anodically electrodeposited thin germanium films can be effectively adjusted by tuning the electrodeposition parameters.Germanium thin films deposited on various substrates are known to give rise to unusual and interesting properties that are important from the point of view of both optoelectronic and microelectronic applications. 1-6 As the film thickness decreases, the surface to volume ratio increases and affects the complexity of the surface morphology. Thus, amorphous germanium with dangling bonds and grain boundaries as well as nanocrystalline and microcrystalline grains of random orientation are known to arise. 1,7 The sizes of the particles and the surface structures are critical for thin film properties such as photoluminescence ͑PL͒, 1,2,6 electrical resistance, 1 etc. It has been shown that the bandgap of germanium nanocrystalline thin films increases when the film thickness decreases from 200 to 5 nm. 1 In addition, as the thickness decreases the film gradually transforms from a continuous to a more and more discontinuous one, and this results in lower conductivity as the discontinuity makes it difficult for electrons with sufficient thermal energy to populate conduction levels. Similarly, the decreasing thickness causes systematic changes in the optoelectronic properties and a gradual shift to higher energies in the PL peak maxima and absorption edges. Studies pertaining to germanium nanocrystals embedded in a GeO 2 matrix show size dependent shifts of the PL peaks which occur in the visible region of the electromagnetic spectrum. 2 Other studies of anodized porous germanium with 3-10 nm nanocrystallites show that the PL spectrum has a broad peak in the near infrared ͑NIR͒ and that surface oxidation induces a new emission band centered in the visible region of the spectrum. 8 Electrodeposition, also known as electrocrystallization, is a well known technique for the preparation of crystalline semiconductors. 9 It attracted considerable interest in the 1980s and 1990s as an approach for the production of economically viable solar cells. It is inexpensive, can yield large area samples, and is readily scalable for industrial produc...

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Photoluminescence of nanocrystals embedded in oxide matrices

Cited by 2 publications

References 10 publications

Modeling and Simulation of Multipumping Photovoltaic Irrigation Systems

Modeling and Simulation of Multipumping Photovoltaic Irrigation Systems

Structural, Vibrational, and Optical Characterization of Anodically Electroplated Germanium Thin Films

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