Interfacing Low‐Temperature Atomic Layer Deposited TiO2 Electron Transport Layers with Metal Electrodes. Issue 8 (26th February 2020)

• Record Type: Journal Article
• Authors: Tan, Wanliang; Bowring, Andrea R.; Babadi, Aein S.; Meng, Andrew C.; Tang‐Kong, Robert; McGehee, Michael D.; McIntyre, Paul C.
• Is Part Of: Advanced materials interfaces. Volume 7:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-02-26
• Subjects: interface -- low‐temperature titanium oxide -- metal -- Schottky barrier; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.201902054
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: Low‐temperature atomic layer deposited (ALD) TiO2 is an electron transport layer that is relatively unreactive with mixed halide perovskite semiconductors. This amorphous, ALD‐grown metal oxide is typically interposed between the perovskite layer and a low work function metal electrode, prompting interest in the electronic and chemical structure of the resulting TiO2 /metal interface. Here, the interfaces between TiO2 and two common metal low work function electrodes, polycrystalline thin films of silver and aluminum are studied. It is found that a Schottky barrier forms between Ag and low‐temperature ALD‐grown TiO2, consistent with the observed solar cell current–voltage characteristics, and confirmed by in situ measurement of Ag deposition‐induced core level shifts in X‐ray photoelectron spectra and barrier height extraction from temperature‐dependent current–voltage data. On the other hand, Al reacts chemically with the surface of TiO2 during its deposition. The resulting interface acts as an Ohmic contact, due to the apparent oxygen vacancy doping of the underlying ALD‐TiO2 . These findings provide lessons for metal electrode selection in future halide perovskite device structures. Abstract : A detailed study of the interfaces between TiO2 and two metal electrodes, polycrystalline thin film silver and aluminum, is reported. A Schottky barrier is observed between the Ag electrode and the low‐temperature ALD TiO2, whereas an Ohmic contact forms between the Al electrode and ALD TiO2 . The mechanisms underlying these findings provide lessons for electrode design in halide perovskite devices.