Indium tin oxide obtained by high pressure sputtering for emerging selective contacts in photovoltaic cells. (January 2022)

• Record Type: Journal Article
• Authors: Caudevilla, D.; García-Hemme, E.; San Andrés, E.; Pérez-Zenteno, F.; Torres, I.; Barrio, R.; García-Hernansanz, R.; Algaidy, S.; Olea, J.; Pastor, D.; del Prado, A.
• Is Part Of: Materials science in semiconductor processing. Volume 137(2022)
• Publication Date: 2022-01
• Subjects: High Pressure Sputtering -- photovoltaics -- transparent conductors -- Selective contacts; Semiconductors -- Periodicals; Integrated circuits -- Materials -- Periodicals; Semiconducteurs -- Périodiques; Circuits intégrés -- Matériaux -- Périodiques; Electronic journals; 621.38152
• DOI: 10.1016/j.mssp.2021.106189
• Languages: English
• ISSNs: 1369-8001

Abstract

Abstract: This article studies the physical and electrical behavior of indium tin oxide layers (ITO) grown by an unconventional technique: High Pressure Sputtering (HPS), from a ceramic ITO target in a pure Ar atmosphere. This technique has the potential to reduce plasma induced damage to the samples. The aim is to obtain, at low temperature via HPS, good quality transparent conductive oxide layers for experimental photovoltaic cells with emerging selective contacts such as transition metal oxides, alkaline metal fluorides, etc. We found that the resistivity of the films was strongly dependent on Ar pressure. To obtain device-quality resistivity without intentional heating during deposition a pressure higher than 1.0 mbar was needed. These films deposited on glass were amorphous, presented a high electron mobility (up to 45 cm 2 V −1 s −1 ) and a high carrier density (2.9 × 10 20 cm −3 for the sample with the highest mobility). The optimum Ar pressure range was found at 1.5–2.3 mbar. However, the resistivity degraded with a moderate annealing temperature in air. Finally, the feasibility of the integration with photovoltaic cells was assessed by depositing on Si substrates passivated by a-Si:H. The film deposited at 1.5 mbar was uniform and amorphous, and the carrier lifetime obtained was 1.22 ms with an implied open circuit voltage of 719 mV after a 215 °C air anneal. The antireflective properties of HPS ITO were also demonstrated. These results show that ITO deposited by HPS is adequate for the research of solar cells with emerging selective contacts. Graphical abstract: Image 1 Highlights: Sputtering ITO at high pressure good properties for emerging selective contacts. Resistivity decreases with increasing pressure, small dependence on rf power. Good transparency in the visible region with a bandgap of 3.7 ± 0.1 eV. ITO/a-Si:H/Si/a-Si:H long lifetimes, iVOC of 710 mV, antireflective.