Atomic Layer Deposition of PbI 2 Thin Films

Abstract

Atomic layer deposition (ALD) enables the deposition of numerous materials in thin film form, yet there are no ALD processes for metal iodides. Herein, we demonstrate an ALD process for PbI 2 , a metal iodide with a two-dimensional (2D) structure that has applications in areas such as photodetection and photovoltaics. This process uses lead silylamide Pb(btsa) 2 and SnI 4 as precursors and works at temperatures below 90 °C, on a variety of starting surfaces and substrates such as polymers, metals, metal sulfides, and oxides. The starting surface defines the crystalline texture and morphology of the PbI 2 films. Rough substrates yield porous PbI 2 films with randomly oriented 2D layers, whereas smooth substrates yield dense films with 2D layers parallel to the substrate surface. Exposure to light increases conductivity of the ALD PbI 2 films which enables their use in photodetectors. The films can be converted into a CH 3 NH 3 PbI 3 halide perovskite, an important solar cell absorber material. For various applications, ALD offers advantages such as ability to uniformly coat large areas and simple means to control film thickness. We anticipate that the chemistry exploited in the PbI 2 ALD process is also applicable for ALD of other metal halides.