Deposition technology of transparent conducting oxide (TCO) thin films is critical for high performance of optoelectronic devices. Solution-based fabrication methods can result in substantial cost reduction and enable broad applicability of the TCO thin films. Here we report a simple and highly effective solution process to fabricate indium-tin oxide (ITO) thin films with high uniformity, reproducibility, and scalability. The ITO films are highly transparent (90.2%) and conductive (ρ = 7.2 × 10(-4) Ω·cm) with the highest figure of merit (1.19 × 10(-2) Ω(-1)) among all the solution-processed ITO films reported to date. The high transparency and figure of merit, low sheet resistance (30 Ω/sq), and roughness (1.14 nm) are comparable with the benchmark properties of dc sputtering and can meet the requirements for most practical applications.
Electrical and optical properties of transparent conducting oxides (TCOs) are of essential importance for optoelectronics. Electronic structures are keys to the understanding of these properties. The geometrical and electronic structures of body-centered cubic In 2 O 3 n-typedoped by Group 14 and fifth-period main group elements (Sb, Te and I) are systematically investigated. The calculated electronic structures reveal a good hybridization between the O-2p states and the s-states of Si, Ge and Sn, resulting in superior electronic properties, such as a freeelectron-like band feature, a large band width (> 2 eV), a low effective mass (m*=0.2m 0 ) and a high electron group velocity (≥8.35×10 5 m/s). The charge localization on the dopants leads to inferior electronic properties of In 2 O 3 doped by other dopants. The calculated defect formation energy indicates that the formation of both neutral and +1 charge state Sn is spontaneous in indium oxide.
Taking a robust zirconium-based metal–organic
framework,
UiO-66, as a prototype, functional postmodification via the versatile
Cu(I)-catalyzed azide–alkyne “click” reaction
was carried out, and sulfonic acid groups were successfully grafted
into its skeleton. Characterizations revealed that the MOF network
was still well maintained after being treated by “clicked”
modification. Investigations by electrochemical impedance spectroscopy
measurements revealed that its proton conductivity increases exponentially
up to 8.8 × 10–3 S cm–1 at
80 °C and 98% RH, while those of the UiO-66 and UiO-66-NH2 are only 6.3 × 10–6 and 3.5 ×
10–6 S cm–1, respectively, at
the same condition. Additionally, the continuous test shows it possesses
long-life reusability. Such a remarkable enhancement on the proton
conductivities and high performance in long-life reusability of the
resultant MOF demonstrated that the “click” reaction
is a facile reaction in postmodification of robust porous materials
toward targeted applications, with which highly promising candidates
of proton-conductive electrolytes for applying in proton-exchange-membrane
(PEM) fuel cell can be achieved.
Surface modification
of ITO films is important for their applications
in optoelectronics. Herein, trimesic acid was used to modify polycrystalline
ITO nanoparticles. Spectroscopic results indicate the formation of
carboxylate on the ITO nanoparticle surfaces upon modification. Density
functional theory calculations reveal an upstanding adsorption structure
of the acid molecule on the ITO (111) surface and the formation of
a carboxylate surface species. The dissociative chemisorption of trimesic
acid on the selected surface was found to be thermodynamically exothermic
and kinetically facile. We show that the surface-modified ITO nanoparticles
are capable of effectively enhancing the charge-transfer rate and
substantially boosting electrocatalytic effect toward redox of ferrocene
via a π–π interaction between ferrocene and the
adsorbate.
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