Cesium iodide (CsI) is a well-established scintillator material that also serves as a precursor for all-inorganic halide perovskite solar absorbers, such as CsPbI 3 . However, the lack of conformal and scalable methods to deposit halide perovskite thin films remains a major challenge on their way to commercialization. In this work, we employ atomic layer deposition (ALD) as the key method due to its inherent scalability to large areas and complex-shaped surfaces. We demonstrate two new ALD processes for the deposition of CsI and CsPbI 3 thin films. The CsI process relies on cesium bis(trimethylsilyl) amide (Cs(btsa)) and tin(IV) iodide (SnI 4 ) as precursors and yields high-purity, uniform, and phase-pure thin films. This process works in a wide temperature range (140−350 °C) and exhibits a large growth per cycle value (GPC) of 3.3 Å (85% of a CsI monolayer). Furthermore, we convert CsI into CsPbI 3 perovskite by exposing a CsI film to our earlier PbI 2 ALD process. We demonstrate the deposition of phase-pure γor δ-CsPbI 3 perovskite thin films, depending on the applied deposition temperature and number of PbI 2 cycles. We believe that the ALD-based approach described in this work will offer a viable alternative for depositing perovskite thin films in applications that involve complex high aspect ratio structures or large substrate areas.

In this paper we present laboratory-scale x-ray absorption spectroscopy applied to the research of nanometer-scale thin films. We demonstrate the Cu K edge x-ray absorption near edge structure (XANES) and...

Copper iodide (CuI) is a high‐performance p‐type transparent semiconductor that can be used in numerous applications, such as transistors, diodes, and solar cells. However, the lack of conformal and scalable methods to deposit CuI thin films limits its establishment in applications that involve complex‐shaped and/or large substrate areas. In this work, atomic layer deposition (ALD) is employed to enable scalable and conformal thin film deposition. A two‐step approach relying on ALD of CuO and its subsequent conversion to CuI via exposure to HI vapor at room temperature is demonstrated. The resulting CuI films are phase‐pure, uniform, and of high purity. Furthermore, CuI films on several substrates such as Si, amorphous Al2O3, n‐type TiO2, and γ‐CsPbI3 perovskite are prepared. With the resulting n‐TiO2/p‐CuI structure, the easy and straightforward fabrication of a diode structure as a proof‐of‐concept device is demonstrated. Moreover, the successful deposition of CuI on γ‐CsPbI3 proves the compatibility of the process for using CuI as the hole transport layer in perovskite solar cell applications in the nip‐configuration. It is believed that the ALD‐based approach described in this work will offer a viable alternative for depositing transparent conductive p‐type CuI thin films in applications that involve complex high aspect ratio structures and large substrate areas.

Atomic layer deposition offers outstanding film uniformity and conformality on substrates with high aspect ratio features. These qualities are essential for mixed-halide perovskite films applied in tandem solar cells, transistors...