{"id":62,"date":"2010-01-18T13:21:28","date_gmt":"2010-01-18T18:21:28","guid":{"rendered":"http:\/\/blogs.vassar.edu\/magnes\/?page_id=62"},"modified":"2012-01-16T11:58:29","modified_gmt":"2012-01-16T16:58:29","slug":"sarah-laird","status":"publish","type":"page","link":"https:\/\/pages.vassar.edu\/magnes\/advanced-electromagnetism-phys-341\/sarah-laird\/","title":{"rendered":"Electrochormism"},"content":{"rendered":"

Electrochromism<\/strong><\/p>\n

Blog Proposal<\/em><\/p>\n

Just as a refresher, this was my proposal: \u00a0I plan on studying electrochromism for my blog project. Electrochromism is defined as a reversible optical change in a material that is induced by the application of an electric potential. \u00a0By altering the applied voltage, you can produce different colors. \u00a0I did a project on this last year and I plan on using the data I collected to compare applied voltage to resulting color. \u00a0Griffiths talks about skin depth, which is a measurement of how far a wave penetrates into a conductor. \u00a0I am going to play with this formula on mathematica. \u00a0Using my data, I will be able to determine the current based on the voltage and resistivity and as a final calculation, I am going to graph current versus skin depth.<\/p>\n

Introduction<\/em><\/p>\n

Electrochromism is defined as a reversible optical change in a material that is induced by the application of an electric potential.\u00a0\u00a0 Tungsten oxide and other transition metal oxides of NI, Co, and Ir, have been extensively studied and shown to exhibit colors throughout the visible spectrum.\u00a0 Conductive organic polymers have also been shown to exhibit electrochromatic behavior, and are advantageous because they are usually transparent in the ground state.\u00a0 Organic polymers are suitable for applications in semiconductors, transistors and LEDs.\u00a0 Organic polymers whose band energy gaps are small, so that the energy needed to release the electron charge carrier can be smaller, are suitable for the organic layer of electrochromatic devices.<\/p>\n

Here is a short clip demonstrating electrochromism:<\/p>\nhttp:\/\/www.youtube.com\/watch?v=VmKfgeqBAKI<\/a>\n

What is actually happening?<\/p>\n

\"Picture<\/p>\n

Constructing the device<\/em><\/p>\n

Electrochromism occurs when there is an oxidation or reduction reaction between the organic polymer layer and the electrolyte layer. Through chemical doping, (p-doping for oxidation and n-doping for reduction) the organic layer displays characteristics of increased conductivity and reversible optical changes.<\/p>\n

The device consisted of two Indium Tin Oxide coated glass plates with a layer of electrolyte gel sandwiched between them.\u00a0 One of the ITO sides was coated with a layer of polyaniline (PAN) and adhered to the slide with a thin layer of \u00a0polyvinyle alcohol (PVA) film.<\/p>\n

This is what our final device looked like:<\/p>\n

\"Screen<\/div>\n

The final structure consisted of:\u00a0 glass\/ITO\/PVA\/PAN\/electrolyte gel\/ITO\/glass.\u00a0 Two copper leads were inserted; one between the electrolyte and the ITO and the other between the electrolyte\u00a0 and the PAN film.\u00a0 With these leads, we were able to apply a voltage cross the device.<\/p>\n

Data and Results<\/em><\/p>\n

After much difficulty, we were able to construct a working device.\u00a0 We measured different voltages and the resulting colors.\u00a0 For my project, I have taken the measured voltage and witnessed color and compared it to the skin depth.<\/p>\n

For this project, I used four equations and made several assumptions.<\/p>\n

Equations:<\/p>\n

\"Picture<\/p>\n

Assumptions:<\/p>\n

Conductivity: \u00a01.68E8 (copper); because we used copper wire to connect the device to the power source.<\/p>\n

\"Picture<\/p>\n

We measured three different samples.\u00a0 Below you will find the data and results from each sample.\u00a0 For each voltage, I predicted what color was being absorbed in the sample based on what color we saw. From here, I calculated the angular frequency, k value and skin depth.\u00a0 I graphed voltage versus skin depth.<\/p>\n

Visible spectrum and corresponding wavelengths.<\/p>\n

\"Picture<\/p>\n

http:\/\/www.gamonline.com\/new\/catalog\/colortheory\/images\/spectrum.gif<\/p>\n

Sample 1:<\/p>\n\n\n\n\n\n\n\n
Voltage (V)<\/td>\nVisible color<\/td>\nAbsorbed color<\/td>\nWavelength (nm)<\/td>\nAngularFrequency<\/td>\n<\/tr>\n
0.3<\/td>\nClear<\/td>\nRed<\/td>\n630<\/td>\n2.99E15<\/td>\n<\/tr>\n
0.95<\/td>\nLight green<\/td>\nOrange\/Yellow<\/td>\n590<\/td>\n3.19E15<\/td>\n<\/tr>\n
1.2<\/td>\nBlue<\/td>\nGreen<\/td>\n530<\/td>\n3.56E15<\/td>\n<\/tr>\n
1.2<\/td>\nPurple<\/td>\nBlue<\/td>\n450<\/td>\n4.19E15<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n\n\n\n\n\n\n
Voltage (v)<\/td>\nk<\/td>\nSkin depth (1\/k)<\/td>\n<\/tr>\n
0.3<\/td>\n5.59E8<\/td>\n5.59E-8<\/td>\n<\/tr>\n
0.95<\/td>\n5.77E8<\/td>\n5.77E-8<\/td>\n<\/tr>\n
1.2<\/td>\n6.11E8<\/td>\n6.11E-8<\/td>\n<\/tr>\n
1.2<\/td>\n6.662E8<\/td>\n6.662E-8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"sample<\/p>\n

Sample 2:<\/p>\n\n\n\n\n\n\n\n
Voltage (V)<\/td>\nVisible color<\/td>\nAbsorbed color<\/td>\nWavelength (nm)<\/td>\nAngularFrequency<\/td>\n<\/tr>\n
0.3<\/td>\nGreen<\/td>\nYellow<\/td>\n580<\/td>\n3.25E15<\/td>\n<\/tr>\n
0.95<\/td>\nBlue<\/td>\nGreen<\/td>\n530<\/td>\n3.55E15<\/td>\n<\/tr>\n
1.2<\/td>\nPurple<\/td>\nBlue<\/td>\n470<\/td>\n4.01E15<\/td>\n<\/tr>\n
1.5<\/td>\nDeep Purple<\/td>\nDeep Blue<\/td>\n440<\/td>\n4.28E15<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n\n\n\n\n\n\n
Voltage (V)<\/td>\nk<\/td>\nSkin depth (1\/k)<\/td>\n<\/tr>\n
0.3<\/td>\n5.84E8<\/td>\n5.84E-8<\/td>\n<\/tr>\n
0.95<\/td>\n6.09E8<\/td>\n6.09E-8<\/td>\n<\/tr>\n
1.2<\/td>\n6.48E8<\/td>\n6.48E-8<\/td>\n<\/tr>\n
1.5<\/td>\n6.69E8<\/td>\n6.69E-8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"Picture<\/p>\n

Sample 3:<\/p>\n\n\n\n\n\n\n\n
Voltage (V)<\/td>\nVisible color<\/td>\nAbsorbed color<\/td>\nWavelength (nm)<\/td>\nAngularFrequency<\/td>\n<\/tr>\n
0.3<\/td>\nBlue\/green<\/td>\nYellow<\/td>\n570<\/td>\n3.31E15<\/td>\n<\/tr>\n
0.95<\/td>\nDark blue<\/td>\nGreen<\/td>\n530<\/td>\n3.55E15<\/td>\n<\/tr>\n
1.2<\/td>\nBlue\/purple<\/td>\nBlue<\/td>\n470<\/td>\n4.01E15<\/td>\n<\/tr>\n
1.3<\/td>\nDark purple<\/td>\nDeep blue<\/td>\n440<\/td>\n4.28E15<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n\n\n\n\n\n\n
Voltage (V)<\/td>\nk<\/td>\nSkin depth (1\/k)<\/td>\n<\/tr>\n
0.3<\/td>\n5.89E8<\/td>\n5.89E-8<\/td>\n<\/tr>\n
0.95<\/td>\n6.09E8<\/td>\n6.09E-8<\/td>\n<\/tr>\n
1.2<\/td>\n6.48E8<\/td>\n6.48E-8<\/td>\n<\/tr>\n
1.3<\/td>\n6.69E8<\/td>\n6.69E-8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"Picture<\/p>\n

According to Griffith, for a\u00a0 good conductor (like the elctrolyte used) you can assume that:<\/p>\n

\"Picture<\/p>\n

and then you are left with a k value that is roughly equal to:<\/p>\n

\"Picture<\/p>\n

Everything in this equation is a constant, so kappa depends on the square root of omega.<\/p>\n

\"Picture<\/p>\n

This is a mathetica graph of\u00a0 the square root of omega.\u00a0 As you can see, this vaguely looks like the three graphs I have above.\u00a0 I have set voltage as the y-axis and the skin depth as the x-axis, and the slope is equal to:<\/p>\n

Voltage\/skin depth<\/p>\n

and d = 1\/k<\/p>\n

therefore, voltage grows as\u00a0 kappa increases and kappa is proportional to the squre root of omega.<\/p>\n

Real Life:<\/p>\n

Electrochromic cells are currently being used in \u201csmart windows\u201d to control the amount of light that passes through the window.\u00a0 By switching on a power supply, the window will become tinted.\u00a0 This application is also being used in cars.\u00a0 The idea is that tinted windows are dangerous at night when visibility is already limited. \u00a0\u00a0The driver will be able to turn on a power supply and tint the car windows depending on the exterior light conditions.<\/p>\n

References:<\/p>\n

\"Picture<\/p>\n

———————————————————————————————————-<\/p>\n

Here is my TM rectangular waveguide.<\/p>\n

Waveguide<\/a><\/p>\n

———————————————————————————————————–<\/p>\n

wave stuff.<\/a><\/p>\n

———————————————————————————————————–<\/p>\n

Journal Summary<\/p>\n

I use my journal as a workspace to reflect upon problems and questions that have come up during class. \u00a0Mostly, I use my journal to reorganize my notes and to begin rough work on homework problems. \u00a0By reworking class problems and adding additional information into my journal, I have been using my journal as a study guide. \u00a0Even though my journal helped me to study for the midterm, I think most of the work I am putting into it is a little redundant. \u00a0Flipping through my past entries, I have found that the questions and concerns I did have were either answered during a class or I was able to figure them out through the homework problems. \u00a0I think I get more out of homework problems, class lectures and peer discussions then I do from the journal<\/p>\n","protected":false},"excerpt":{"rendered":"

Electrochromism Blog Proposal Just as a refresher, this was my proposal: \u00a0I plan on studying electrochromism for my blog project. Electrochromism is defined as a reversible optical change in a material that is induced by the application of an electric potential. \u00a0By altering the applied voltage, you can produce different colors. \u00a0I did a project […]<\/p>\n","protected":false},"author":98,"featured_media":0,"parent":9,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-62","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/pages\/62","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/users\/98"}],"replies":[{"embeddable":true,"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/comments?post=62"}],"version-history":[{"count":24,"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/pages\/62\/revisions"}],"predecessor-version":[{"id":4083,"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/pages\/62\/revisions\/4083"}],"up":[{"embeddable":true,"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/pages\/9"}],"wp:attachment":[{"href":"https:\/\/pages.vassar.edu\/magnes\/wp-json\/wp\/v2\/media?parent=62"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}