Exploring the Origin of Phase-Transformation Kinetics of CsPbI₃ Perovskite Nanocrystals Based on Activation Energy Measurements

Abstract

Perovskite α-CsPbI3 nanocrystals (NCs) with a high fluorescence quantum yield (QY) typically undergo a rapid phase transformation to a low-QY δ-CsPbI3 phase, thus limiting their optoelectronic applications. In this study, organic molecule hexa­methyl­di­sila­thiane (HMS) is used as a unique surfactant to greatly enhance the stability of the cubic phase of CsPbI3 NCs (HMS-CsPbI3) under ambient conditions. The reaction kinetics of the phase transformation of CsPbI3 NCs are systemically investigated through in situ photoluminescence (PL), X-ray diffraction, and transmission electron microscope (TEM) measurements under moisture. The activation energy of HMS-CsPbI3 NCs is found to be 14 times larger than that of CsPbI3 NCs capped by olyelamine (OLA-CsPbI3 NCs). According to density functional theory calculations, the bonding between HMS and CsPbI3 NCs is stronger than that between OLA and CsPbI3 NCs, preventing the subsequent phase transformation. Our study presents a clear pathway for achieving highly stable CsPbI3 NCs for future applications.

Octahedral distortion driven by CsPbI3 nanocrystal reaction temperature – the effects on phase stability and beyond

“…We attribute the highest PLQY of 96% for 135@NCs to their longest excited state lifetime, as will be detailed in following section. Note that this (96%) is one of the highest PLQY among all the reported values for pristine CsPbI 3 NCs (which are typically below 90% [28][29][30] ). All the samples exhibit narrow emission bands, indicating that the size distribution of as-formed NCs can be precisely controlled.…”

Mg2+-Assisted Passivation of Defects in CsPbI3 Perovskite Nanocrystals for High-Efficiency Photoluminescence

“…Usually, long-chain ligands such as oleylamine (OLA) and oleic acid (OA) are easily detached from the surface of NCs during the purification process, which leads to poor stability. It is reported that optical properties and stability of CsPbI 3 NCs in harsh environments can be improved by using short-chain ligands or ligands with multiple functional groups, such as hexamethyldisilathiane (HMS), sodium dodecyl sulfate (SDS), didodecyldimethylammonium bromide (DDAB), 2,2′-iminodibenzoic acid (IDA), − etc. However, the dynamic bonding process between the ligand and NC surface is not very clear, and the preparation process of ligand exchange is complex, which requires appropriate synthesis conditions and then brings difficulties to the preparation of efficient and stable CsPbI 3 NCs …”

Laser-accelerated phase transformation in cesium lead iodide perovskite

“…To further understand the influence of laser illumination, systematic power-and wavelengthdependent studies are performed on the LAPT process. Given that moisture is known to accelerate the high-T to low-T phase transformation, 5,13,14,21 we first investigate LAPT under different moisture levels (Figure 3D). We find that moisture and laser exhibit a coupling effect.…”