Surface passivation and carrier selectivity of the thermal-atomic-layer-deposited TiO2 on crystalline silicon

Maksym Plakhotnyuk, Nadine Schüler, Evgeniy Shkondin, Ramachandran Ammapet Vijayan, Sangaravadivel Masilamani, Muthubalan Varadharajaperumal, Andrea Crovetto, Ole Hansen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Here, we demonstrate the use of an ultrathin TiO2 film as a passivating carrier-selective contact for silicon photovoltaics. The effective lifetime, surface recombination velocity, and diode quality dependence on TiO2 deposition temperature with and without a thin tunneling oxide interlayer (SiO2 or Al2O3) on p-type crystalline silicon (c-Si) are reported. 5-, 10-, and 20-nm-thick TiO2 films were deposited by thermal atomic layer deposition (ALD) in the temperature range of 80–300 °C using titanium tetrachloride (TiCl4) and water. TiO2 thin-film passivation layers alone result in a lower effective carrier lifetime compared with that with an interlayer. However, SiO2 and Al2O3 interlayers enhance the TiO2 passivation of c-Si surfaces. Further annealing at 200 °C in N2 gas enhances the surface passivation quality of TiO2 tremendously. From these findings, design principles for TiO2–Si heterojunction with optimized photovoltage, interface quality, and electron extraction to maximize the photovoltage of TiO2–Si heterojunction photovoltaic cells are formulated. Diode behaviour was analysed with the help of experimental, analytical, and simulation methods. It is predicted that TiO2 with a high carrier concentration is a preferable candidate for high-performance solar cells. The possible reasons for performance degradation in those devices with and without interlayers are also discussed.
    Original languageEnglish
    Article number08MA11
    JournalJapanese Journal of Applied Physics
    Volume56
    Issue number8S2
    Number of pages8
    ISSN0021-4922
    DOIs
    Publication statusPublished - 2017

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