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| {{distinguish|Quantum yield}}
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| [[Image:Quantum efficiency graph for WFPC2-en.svg|thumb|right|300px|A graph showing variation of quantum efficiency with wavelength of a CCD chip in the [[Hubble Space Telescope]]'s [[Wide Field and Planetary Camera 2]].]] | | [http://linux268.php.Xdomain.jp/profile/chzempel xdomain.jp]The cheapest [http://Www.Dinnerfor6.com/home/blog/view/97751/msi-gaming-laptops-philippines-and-love-have-six-things-in-common version] ships with the Intel Centrino processor, which can be old, pitiful for games and disqualifies it immediately. There continues to be talk in some with the [http://www.jfv-staleke.de/benefits-of-cheap-refurbished-laptops-like-dell-latitude/ cheap gaming laptops under 600] gaming forums about heat difficulty with Ivy Bridge processors, particularly if they're over-clocked.<br><br>Scope out bios in magazines and also on book dust sides [[https://support.corset-story.com/entries/72428376-Gaming-Laptops-Four-Factors-To-Check-Before-Selecting support.corset-story.com]] jackets; practice by copying another person's bio. I enjoy lists too, but nothing can beat mind maps for giving a sense that you're in control of your respective writing topic. [http://support.planbtravel.com.au/entries/39029389-Acer-Aspire-3004wlci-A-Quick-Review Alienware M15X] [http://Se.ce.Pusan.ac.kr/xe/eng_notice/5325690 gaming laptops] under 500 dollars I always ordered great gaming laptops under 1000 papers in such instances and haven't experienced any ethical issues with that. Figure out how much your time is worth and hang the price accordingly. |
| The word '''quantum efficiency (QE)''' may apply to '''incident photon to converted electron (IPCE) ratio''',<ref>{{cite journal|last=Shaheen|first=Sean|title=2.5% efficient organic plastic solar cells|journal=Applied Physics Letters|year=2001|volume=78|issue=6|doi=10.1063/1.1345834|url=http://apl.aip.org/resource/1/applab/v78/i6/p841_s1?bypassSSO=1|accessdate=20 May 2012|bibcode = 2001ApPhL..78..841S }}</ref> of a [[photosensitivity|photosensitive device]] or it may refer to the [[Tunnel_magnetoresistance|TMR effect]] of a Magnetic Tunnel Junction. In a [[charge-coupled device]] (CCD) is the percentage of [[photon]]s hitting the device's photoreactive surface that produce [[charge carrier]]s. It is measured in [[electron]]s per photon or [[ampere|amps]] per [[watt]].<ref>[http://www.photonics.com/Directory/Dictionary/Definition.aspx?type=2&DictionaryID=6488 Definition of quantum efficiency in Photonics Dictionary]</ref> QE is a measurement of a device's electrical sensitivity to light. Since the energy of a photon is [[proportionality (mathematics)#Inversely proportional|inversely proportional]] to its [[wavelength]], QE is often measured over a range of different wavelengths to characterize a device's [[efficiency]] at each photon energy level. The QE for photons with energy below the [[band gap]] is zero. Photographic film typically has a QE of much less than 10%,<ref name=Trager200>{{cite book|last=Träger|first=Frank|title=Handbook of Lasers and Optics|year=2012|publisher=Springer|location=Berlin Heidelberg|isbn=9783642194092|pages=601|pages=603|url=http://books.google.pl/books?id=Ad5G1HWtDRgC&lpg=PP1&pg=PA603#v=onepage&q&f=false}}</ref> while CCDs can have a QE of well over 90% at some wavelengths.
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| ==Quantum efficiency of solar cells==
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| [[Image:Solarcellige-en.svg|thumb|right|400px|A graph showing variation of internal quantum efficiency, external quantum efficiency, and reflectance with wavelength of a crystalline silicon solar cell.]]
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| A solar cell's quantum efficiency value indicates the amount of current that the cell will produce when irradiated by photons of a particular wavelength. If the cell's quantum efficiency is [[integral|integrated]] over the whole [[sunlight|solar electromagnetic spectrum]], one can evaluate the amount of current that the cell will produce when exposed to sunlight. The ratio between this energy-production value and the highest possible energy-production value for the cell (i.e., if the QE were 100% over the whole spectrum) gives the cell's overall [[solar cell efficiency|energy conversion efficiency]] value. Note that in the event of [[multiple exciton generation]] (MEG), quantum efficiencies of greater than 100% may be achieved since the incident photons have more than twice the [[band gap]] energy and can create two or more electron-hole pairs per incident photon.
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| ===Types of quantum efficiency===
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| Two types of quantum efficiency of a solar cell are often considered:
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| *'''External Quantum Efficiency (EQE)''' is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy ''shining on the solar cell from outside'' (incident photons).
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| *'''Internal Quantum Efficiency (IQE)''' is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy that shine on the solar cell from outside ''and'' are absorbed by the cell.
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| The IQE is always larger than the EQE. A low IQE indicates that the active layer of the solar cell is unable to make good use of the photons. To measure the IQE, one first measures the EQE of the solar device, then measures its transmission and reflection, and combines these data to infer the IQE.
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| :<math> \text{EQE} = \frac{\text{electrons/sec}}{\text{photons/sec}}= \frac{\text{current}/\text{(charge of 1 electron)}}{(\text{total power of photons})/(\text{energy of one photon})}</math>
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| :<math> \text{IQE} =
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| \frac{\text{EQE}}{\text{Total Absorption}}=
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| \frac{\text{EQE}}{\text{1-Reflection-Transmission}}
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| </math>
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| The external quantum efficiency therefore depends on both the [[Absorption (electromagnetic radiation)|absorption]] of light and the collection of charges. Once a photon has been absorbed and has generated an electron-hole pair, these charges must be separated and collected at the junction. A "good" material avoids charge recombination. Charge recombination causes a drop in the external quantum efficiency.
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| The ideal quantum efficiency graph has a [[Boxcar function|square shape]], where the QE value is fairly constant across the entire spectrum of wavelengths measured. However, the QE for most solar cells is reduced because of the effects of recombination, where charge carriers are not able to move into an external circuit. The same mechanisms that affect the collection probability also affect the QE. For example, modifying the front surface can affect carriers generated near the surface. And because high-energy (blue) light is absorbed very close to the surface, considerable recombination at the front surface will affect the "blue" portion of the QE. Similarly, lower energy (green) light is absorbed in the bulk of a solar cell, and a low diffusion length will affect the collection probability from the solar cell bulk, reducing the QE in the green portion of the spectrum. Generally, solar cells on the market today do not produce much electricity from [[ultraviolet]] and [[infrared]] light (<400 nm and >1100 nm wavelengths, respectively); this light is either filtered out or absorbed by the cell, heating the cell. That heat is wasted energy, and could lead to damage to the cell.<ref>[http://www.autobloggreen.com/2007/08/21/silicon-nanoparticle-film-can-increase-solar-cell-performance/ Silicon nanoparticle film can increase solar cell performance]</ref>
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| '''Quantum efficiency of Image Sensors''' :
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| Quantum efficiency (QE) is the fraction of photon flux that contributes to the photocurrent in a photodetector or
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| a pixel.Quantum efficiency is one of the most important parameters used to evaluate the quality of a detector and is often called the spectral response to reflect it’s wavelength dependence. It is defined as the number of signal electrons created per incident photon. In some cases it can exceed 100% (i.e. more than one electron created per incident photon).
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| ==Spectral responsivity==
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| [[responsivity|Spectral responsivity]] is a similar measurement, but it has different units: [[ampere]]s per [[watt]] (A/W); (i.e. how much [[electric current|current]] comes out of the device per incoming photon of a given energy and wavelength).<ref>[http://www.photonics.com/Directory/Dictionary/Definition.aspx?type=2&DictionaryID=6750 Definition of responsivity in Photonics Dictionary]</ref> Both the quantum efficiency and the responsivity are functions of the photons' wavelength (indicated by the subscript λ).
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| To convert from responsivity (''R<sub>λ</sub>'', in A/W) to QE<sub>λ</sub><ref>A. Rogalski, K. Adamiec and J. Rutkowski, ''Narrow-Gap Semiconductor Photodiodes'', SPIE Press, 2000</ref> (on a scale 0 to 1):
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| :<math>QE_\lambda=\frac{R_\lambda}{\lambda}\times\frac{h c}{e}\approx\frac{R_\lambda}{\lambda} {\times} (1240\;{\rm W}\cdot {\rm nm/A}) </math>
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| where ''λ'' is in [[nanometre|nm]], ''h'' is the [[Planck constant]], ''c'' is the [[speed of light]] in a vacuum, and ''e'' is the [[elementary charge]].
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| ===Determination===
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| :<math>QE_\lambda=\eta =\frac{N_e}{N_\nu}</math>
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| where <math>N_e</math> = number of electrons produced, <math>N_\nu</math> = number of photons absorbed.
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| :<math>\frac{N_\nu}t = \Phi_o \frac{\lambda}{hc}</math>
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| Assuming each photon absorbed in the depletion layer produces a viable electron-hole pair, and all other photons do not,
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| :<math>\frac{N_e}t = \Phi_{\xi}\frac{\lambda}{hc}</math>
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| where ''t'' is the measurement time (in seconds),
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| <math>\Phi_o</math> = incident optical power in watts,
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| <math>\Phi_{\xi}</math> = optical power absorbed in depletion layer, also in watts.
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| ==See also==
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| *[[Counting efficiency]]
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| *[[Detective quantum efficiency|DQE (imaging)]]
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| *[[Solar cell efficiency]]
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| ==References==
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| {{Reflist}}
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| [[Category:Quantum electronics]]
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| [[Category:Spectroscopy]]
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| [[Category:Engineering ratios]]
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| [[Category:Physical quantities]]
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