Solution-processed transparent electrodes from metal oxide nanocrystals for thin film optoelectronics

Content Provider	Semantic Scholar
Copyright Year	2013
Abstract	The aim of this PhD work is to use metal oxide nanocrystals, including aluminum doped zinc oxide (AZO), tin doped zinc oxide (TZO), antimony doped tin oxide (ATO) and indium tin oxide (ITO), as building blocks to form high performance transparent conducting oxide (TCO) films which can be applied to optoelectronic devices by solution processes. AZO nanoparticles with different doping levels are synthesized by a microwave-assisted non-aqueous sol-gel route in benzyl alcohol and subsequently processed into transparent conducting films. The crystal structure, crystal size, shape and doping level of the nanoparticles are analyzed in detail by Rietveld refinement from powder X-ray diffraction (PXRD) data and transmission electron microscopy (TEM). Study of the thermal stability gives evidence that the material is thermally stable up to 600 ◦C. Films are prepared on fused silica substrates by dipcoating from AZO nanoparticle dispersions, followed by a microwave-assisted densification step. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements, the films are homogeneous over large areas with a root mean square roughness of about 10 nm. A minimum resistivity of 2.35 × 10−2 Ω·cm is achieved for a 357 nm thick AZO film with an initial Al-to-Zn mol ratio of 1:9 after post-annealing under N2. The changes of the electrical properties of the films could be well explained on the basis of varying initial doping levels and crystal sizes of the nanoparticle building blocks. The average transmittance of the films in the visible light range is higher than 90 %, and especially for green light it reaches up to 95 %. TZO nanoparticles and films are synthesized by the same method used for AZO. Similar to AZO, the concentration of Sn has a great impact on the electrical properties of the films. A minimum resistivity of 20.3 Ω·cm is obtained for a porous TZO film with initial Sn concentration of 7.5 mol% after annealing in air and post-annealing in N2 at 600 ◦C. The resistivity of this porous film could further be reduced to 2.6 Ω·cm and 0.6 Ω·cm after densification in TZO and AZO reaction solution, respectively. The average optical transmittance of a 400-nm-thick TZO film densified with TZO after the two annealing steps is 91 %. 3 nm diameter ATO nanocrystals with narrow size distrubituon, synthesized by an efficient microwave-assisted nonaqueous sol-gel method as well, are dispersed in tetrahydrofuran (THF) without any additives and processed into films by spin-coating on glass substrates. After thermal
File Format	PDF HTM / HTML
DOI	10.3929/ethz-a-010060532
Alternate Webpage(s)	https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/154290/eth-7973-02.pdf?isAllowed=y&sequence=2
Alternate Webpage(s)	https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/154290/eth-7973-01.pdf?isAllowed=y&sequence=1
Alternate Webpage(s)	https://doi.org/10.3929/ethz-a-010060532
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article