Atomic Layer Deposition of PbI₂ 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 PbI2, 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 SnI4 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 PbI2 films. Rough substrates yield porous PbI2 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 PbI2 films which enables their use in photodetectors. The films can be converted into a CH3NH3PbI3 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 PbI2 ALD process is also applicable for ALD of other metal halides.

PbI2 nanocrystal growth by atomic layer deposition of Pb(tmhd)2 and HI

“…Figure 3c shows hexagonal nanocrystals of PbI2 after 81 cycles of the PbI2 process. The hexagonal shape is consistent with the expected crystal structure for PbI2 and in agreement with previous literature reports [25], [40]. After 162 cycles, the crystals have grown in diameter while maintaining a hexagonal shape (Figure 3d).…”

Chemical Vapor Deposited Mixed Metal Halide Perovskite Thin Films

“…Refer to Table 1 below for layer-by-layer details. The stoichiometry of the PbI 2 film reported in this work corresponds to that reported by Popov et al [70] and Tsevas et al [71]. etry of 3.50 × 10 22 atoms/cm 2 and Si0.19O0.72Al0.05Ba0.04As0.003, which correlates to what was obtained by Kumar et al [72].…”

Optical Properties of Ion Accumulation Areas in MAPbX3 Single Crystals

“…I 2 vapor generated by material decomposition can be trapped in a cavity, while the power density of the excitation laser increases to a high level. [63]…”