Processing and characterization of transparent electrode materials
Kuupäev
2017-07-04
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Läbipaistvad elektrit juhtivad kiled on olulised komponendid moodsates optoelektroonikaseadmetes, nagu päikesepaneelid, valgusdioodid ja plasmapaneelid. Sellised kiled peavad olema hea elektrijuhtivusega aga säilitades samal ajal ka läbipaistvuse vajalikus optilises diapasoonis. Eksisteerib palju materjale, mis on kas head elektrijuhid või hea optilise läbipaistvusega, kuid ainult vähesed materjalid ilmutavad samaaegselt mõlemat omadust. Hetkel põhiline tööstuses kasutatav materjal on indium-tina-oksiid (ITO). Paraku ITO põhineb indiumil, mis on kallis element. Et alandada elektrit juhtivate läbipaistvate kilede hinda, on vaja välja töötada alternatiivsed materjalid. Nende valmistamine peab põhinema odavatel meetoditel, mis oleks samas sobilikud ka masstootmiseks. Üheks perspektiivseks materjaliks peetakse alumiiniumiga dopeeritud tsinkoksiidi (AZO). Käesolev töö keskendus võrdlemisi odava sool-geel meetodi väljatöötamisele AZO kilede valmistamiseks ning saadud kilede elektriliste ja optiliste omaduste uurimisele. Kuigi AZO kohta on ilmunud mitmeid teadusartikleid, ei ole seniajani avaldatud süstemaatilisi andmeid sool-geel sünteesi parameetrite ja saadud kilede omaduste kohta. Osaliselt tuleneb see sellest, et erinevad autorid kontrollivad sünteesi erinevaid parameetreid ja erinevates diapasoonides ning mitmed olulised eksperimenditingimused on jäetud põhjalikult kirjeldamata. See raskendab sünteesi kordamist. Seetõttu käesolevas töös kõik olemasolevad sool-geel valmistusmeetodid vaadati kriitilise pilguga üle ning tulemusena töötati välja ja viimistleti meetod, mis on ka hästi korratav. Uuriti põhjalikult sool-geel protseduuri kõiki etappe ja proovide kuumtöötlust erinevates keskkondades ning teostati saadud proovide füüsikalis-keemiliste omaduste analüüs. Kilesid valmistati sool-geel lahusest nii vurrkatmise kui ka elektroketruse tehnikatega, võttes eesmärgiks selliste kilede saamise, mis oleksid sobilikumad elektro-optilisteks rakendusteks. Ühtlasi uuriti saadud AZO kilede spetsiifilisi optilisi omadusi nagu fluorestsents ja valguse peegeldumine. Viimaks, demonstreerimaks kilede võimalikku rakendust ja sooritust elektrit juhtivate läbipaistvate pinnakatetena, testiti nende toimimist vedelkristallindikaatorites.
Transparent conductive films are important components of modern optoelectronic devices such as solar cells, light-emitting diodes, and flat panel displays. These films have to be good electrical conductors while at the same time retaining transparency in a desirable optical range. There are many materials that possess separately a good conductivity or a good optical transparency, but only a few materials can combine all these properties at once. Currently the industry standard material is indium tin oxide (ITO). However, ITO is based on indium, which is an expensive element. To decrease the cost of transparent conductive films, alternative materials have to be developed. Additionally they have to be prepared by cheaper methods that are suitable for mass production. Since some prospects are connected with aluminium-doped zinc oxide (AZO) as such alternative material, this research focused on elaboration of relatively inexpensive sol-gel based methods of AZO films preparation and investigation of electrical and optical properties. In spite of certain amount of publications related to the AZO, there is no systematic data about preparation conditions by sol-gel method and resulting film properties. Partly it is caused by the fact that different authors controlled different preparation parameters in different ranges and some important experimental conditions are not fully described. This makes their result hard to reproduce. So in this work existing sol-gel approaches of preparation of AZO films were critically reconsidered and own recipes were elaborated in details whereas a good reproducibility of the method was achieved. We carried out a deep investigation of all the steps of the sol-gel procedure, practical preparation and thermal treatment of samples in different atmospheres, and analysis of their physicochemical properties. The resultant films were deposited by spin-coating and electrospinning methods from sol-gel solution with a goal to obtain films which are more suitable for electro-optical applications. Such specific optical properties as fluorescence and reflectivity of the AZO films were investigated also. Finally, to demonstrate possible application and real performance of the obtained AZO films as transparent conductive coatings, they were tested in the liquid crystal indicators, which are part of liquid crystal displays.
Transparent conductive films are important components of modern optoelectronic devices such as solar cells, light-emitting diodes, and flat panel displays. These films have to be good electrical conductors while at the same time retaining transparency in a desirable optical range. There are many materials that possess separately a good conductivity or a good optical transparency, but only a few materials can combine all these properties at once. Currently the industry standard material is indium tin oxide (ITO). However, ITO is based on indium, which is an expensive element. To decrease the cost of transparent conductive films, alternative materials have to be developed. Additionally they have to be prepared by cheaper methods that are suitable for mass production. Since some prospects are connected with aluminium-doped zinc oxide (AZO) as such alternative material, this research focused on elaboration of relatively inexpensive sol-gel based methods of AZO films preparation and investigation of electrical and optical properties. In spite of certain amount of publications related to the AZO, there is no systematic data about preparation conditions by sol-gel method and resulting film properties. Partly it is caused by the fact that different authors controlled different preparation parameters in different ranges and some important experimental conditions are not fully described. This makes their result hard to reproduce. So in this work existing sol-gel approaches of preparation of AZO films were critically reconsidered and own recipes were elaborated in details whereas a good reproducibility of the method was achieved. We carried out a deep investigation of all the steps of the sol-gel procedure, practical preparation and thermal treatment of samples in different atmospheres, and analysis of their physicochemical properties. The resultant films were deposited by spin-coating and electrospinning methods from sol-gel solution with a goal to obtain films which are more suitable for electro-optical applications. Such specific optical properties as fluorescence and reflectivity of the AZO films were investigated also. Finally, to demonstrate possible application and real performance of the obtained AZO films as transparent conductive coatings, they were tested in the liquid crystal indicators, which are part of liquid crystal displays.
Kirjeldus
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Märksõnad
läbipaistvad elektroodid, metalloksiidkiled, struktuur, elektrilised omadused, optilised omadused, sool-geel protsessid, materjalide katsetamine, electrodes, metal oxide films, structure, electrical properties, optical properties, sol-gel processes, materials testing