Indium-Free Alternative Transparent Conducting Electrodes: An Overview and Recent Developments

Ramarajan, R.; Joseph, D. Paul; Thangaraju, K.; Kovendhan, M.

doi:10.1007/978-3-030-53065-5_5

Cited by 4 publications

(3 citation statements)

References 118 publications

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“…However, the United States Geological Survey (USGS) reported that the world refinery production of indium was only 900 tons in 2020 [7]. The unbalance between the low abundance and the growing demand for indium, forces people to turn their eyes to various alternative indium-free TCOs [3,4,8]. Unfortunately, the performance and scalability of those materials still cannot meet the requirements for applications.…”

Section: Introductionmentioning

confidence: 99%

Transparent conductive SnO2 thin films via resonant Ta doping

et al. 2022

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Transparent conductive oxide (TCO) thin films are highly desired as electrodes for modern flat-panel displays and solar cells. Alternative indium-free TCO materials are highly needed, because of the scarcity and the high price of indium. Based on the mechanism of resonant doping, Ta has been identified as an effective dopant for SnO 2 to achieve highly conductive and transparent TCO. In this work, we fabricated a series of Ta-doped SnO 2 thin films (Sn 1−x Ta x O 2 , x = 0.001, 0.01, 0.02, 0.03) with high conductivity and high optical transparency via a low-cost sol-gel spin coating method. The Sn 0.98 Ta 0.02 O 2 film achieves the highest electrical conductivity of 855 S cm −1 with a carrier concentration of 2.3 × 10 20 cm −3 and high mobility of 23 cm 2 V −1 s −1 . The films exhibit a very high optical transparency of 89.5% in the visible light region. High-resolution X-ray photoemission spectroscopy and optical spectroscopy were combined to gain insights into the electronic structure of the Sn 1−x Ta x O 2 films. The optical bandgaps of the films are increased from 3.96 eV for the undoped SnO 2 to 4.24 eV for the Sn 0.98 Ta 0.02 O 2 film due to the occupation of the bottom of conduction band by free electrons, i.e., the Burstein-Moss effect. Interestingly, a bandgap shrinkage is also directly observed due to the bandgap renormalization arising from many-body interactions. The double guarantee of transparency and conductivity in Sn 1−x Ta x O 2 films and the low-cost growth method provide a new platform for optoelectronic and solar cell applications.

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Section: Introductionmentioning

confidence: 99%

Transparent conductive SnO2 thin films via resonant Ta doping

et al. 2022

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“…The optical transparency and electrical conductivity properties are crucial for their use as transparent conducting electrodes in various optoelectronic devices, depending on their range of sheet resistance values. 6 However, it is challenging to stabilize both the optical transparency and electrical conductivity in a single host material, and there exists a trade-off between these two essential properties. For example, glass is transparent but insulating in nature, whereas metals are conductive but opaque.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, due to the prevailing COVID-19 pandemic, the gap between the supply and demand for ITO has further widened and intense research work is being carried out in search of alternative TCO materials with excellent optical and electrical properties on par with those of ITO. The optical transparency and electrical conductivity of SnO 2 can be increased by doping with suitable dopants such as In, 9 Li, 11 F, 12 Al, 13 Mo, 14 Mn, 15 Co, 16 Ta, 17 W, 18 Nb, 19 and Sb. 20 Among all these dopants, Sb-doped SnO 2 is identified as one of the most promising alternative TCO materials.…”

Section: Introductionmentioning

confidence: 99%

Cost-effective Sb-doped SnO₂ films as stable and efficient alternative transparent conducting electrodes for dye-sensitized solar cells

et al. 2022

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Combining Aqueous Solution Processing and Printing for Fabrication of Flexible and Sustainable Tin Dioxide Ion‐Gated Transistors

Subramanian

Azimi

Santato

et al. 2021

Adv Materials Technologies

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to obtain high-performance crystalline films, these oxides are processed at high temperatures (>350 °C), which are not compatible with flexible electronics. [1a,4] Additionally, the brittle nature of crystalline metal oxides limits their applications in flexible electronics. [4a] SnO 2 is a promising metal oxide for electronics applications due to its abundance, electrical conductivity, and optical transparency, which make it interesting for thin-film transistors, gas sensors, and transparent electrodes. [5] SnO 2 films can be processed via several techniques, such as sputtering, evaporation, pulsed laser deposition, and various solution processing methods. [6] Among these, a single step, low temperature process in aqueous solution would meet the requirements for sustainable and cost-effective flexible electronics. [1a,7] Field effect transistors (FETs) based on SnO 2 films, deposited using physical and chemical methods, exhibited a high field-effect mobility (>100 cm 2 V −1 s −1 ) at an operating voltage below 5 V. [8] Sb-doped SnO 2 showed a mobility of ≈550 cm 2 V −1 s −1 , when the material was deposited by vaporliquid-solid growth, [8d] and ≈158 cm 2 V −1 s −1 , when radio frequency magnetron sputtering was used. [8e] The high mobility of SnO 2 is due to the large overlap of the spherical Sn 5s orbitals in the SnO 2 electronic structure. [8a,9] The charge carrier density (electrons) in SnO 2 can be tuned by creating oxygen vacancies (i.e. deviation of SnO 2 stoichiometry), by unintentional (i.e. impurities during the growth of SnO 2 ) and intentional doping (i.e. metallic dopants such as Ta, Sb on SnO 2 ). [10] By tuning the charge carrier density, the transistor mode of operation can be switched from enhancement to depletion mode. Ohta et al., fabricated FETs based SnO 2 films grown by pulsed laser deposition (400 °C) and investigated the electron transport properties at different thicknesses. The film thickness was found to affect the crystallinity and charge carrier concentration, as well as the performance and operation mode of the transistors. [11] Jang et al., deposited SnO 2 films by UV-ozone assisted solgel (300 °C), which were used as active layers in FETs on flexible polyimide substrates. [12] Lim et al., fabricated flexible SnO 2 FETs on polyethersulfone substrate by direct current reactive magnetron sputtering at room temperature, which did not show Ion-gated transistors (IGTs) are extensively used in chemo-and bio-sensors as well as intelligent sensors, that is, with neuromorphic computing functionality, exploiting their ion to electron convertibility. Metal oxides are attractive as active channel materials in IGTs because of their low-temperature solution processability, ambient stability, and tunable optoelectronic properties. SnO 2 is a low-cost material widely used in thin-film transistors, gas sensors, and transparent electrodes. In this work, films of crystalline SnO 2 nanorods are prepared on flexible substrates using a controlled aqueous growth technique, at 95 °C. The top ...

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Indium-Free Alternative Transparent Conducting Electrodes: An Overview and Recent Developments

Cited by 4 publications

References 118 publications

Transparent conductive SnO2 thin films via resonant Ta doping

Transparent conductive SnO2 thin films via resonant Ta doping

Cost-effective Sb-doped SnO₂ films as stable and efficient alternative transparent conducting electrodes for dye-sensitized solar cells

Combining Aqueous Solution Processing and Printing for Fabrication of Flexible and Sustainable Tin Dioxide Ion‐Gated Transistors

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Indium-Free Alternative Transparent Conducting Electrodes: An Overview and Recent Developments

Cited by 4 publications

References 118 publications

Transparent conductive SnO2 thin films via resonant Ta doping

Transparent conductive SnO2 thin films via resonant Ta doping

Cost-effective Sb-doped SnO2 films as stable and efficient alternative transparent conducting electrodes for dye-sensitized solar cells

Combining Aqueous Solution Processing and Printing for Fabrication of Flexible and Sustainable Tin Dioxide Ion‐Gated Transistors

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Cost-effective Sb-doped SnO₂ films as stable and efficient alternative transparent conducting electrodes for dye-sensitized solar cells