Atomic Layer Deposition for Passivation of Metal Halide Perovskite Materials in Photovoltaic Devices
Karl-Augsutin Zaininger a, Henry J. Snaith a
a Department of Physics, Oxford University
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Poster, Karl-Augsutin Zaininger, 246
Publication date: 11th February 2019

Research into metal-halide-organic perovskite materials has increased dramatically in recent years due to their remarkable performance in optoelectronic devices and their simple and low cost fabri- cation when compared to traditional photovoltaic materials. The transition to large scale adoption of perovskite materials in photovoltaic devices relies on the long-term stability of the materials them- selves as well as their stability at interfaces within the device stack. Defects at these interfaces can reduce both the performance and long term stability of the devices[1], thus passivation of these defects is imperative for the commercialisation and large scale adoption of this technology.

For inverted structures on Nickel Oxide (NiOx), a thermal instability exists at the interface, breaking down the perovskite material at elevated temperatures. A conformal but thin (<1nm) layer of alu- mina (Al2O3) is deposited on NiOx by Atomic Layer Deposition (ALD) in a custom built apparatus and allows charge transport from the perovskite layer to the underlying NiOx while isolating the two layers chemically, preventing degradation due to (photo) chemical reactions.

We also use ALD for passivation on top of the perovskite absorber layer before other transport lay- ers are deposited, as has previously been investigated[2]. Again a thin (<1nm) layer is deposited con- formally over the surface of the perovskite material, passivating any surface defects and providing a chemical barrier against atmospheric degradation. Our non-conventional ALD setup also allows the perovskite films to be sealed in an environment containing the precursor vapours (e.g. trimethylalu- minium and H2O in the case of alumina) and allows for the diffusion of the ALD precursors deeper into the grain boundaries, passivating defects and also preventing transport of degradation inducing species deeper into the film.

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