Atomistic Structures and Energetics of Perovskite Nucleation Pathway During Sequential Deposition Process
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ORIGINAL RESEARCH
Atomistic Structures and Energetics of Perovskite Nucleation Pathway During Sequential Deposition Process Hsin‑An Chen1 · Po‑Hsiang Lee2 · Chun‑Wei Pao1 Received: 16 December 2019 / Revised: 27 August 2020 / Accepted: 1 September 2020 © Korean Multi-Scale Mechanics (KMSM) 2020
Abstract Organometal halide perovskite materials are one of the promising candidates for next generation solar energy conversion and optoelectronics applications. Controlling perovskite film morphologies is the key toward promoting device performance, and the sequential deposition method has been extensively used for fabricating high quality perovskite films. Nevertheless, the conversion processes of perovskite from PbI2 and methylammonium iodide (MAI) precursor remains unclear. In this study, we investigated the nucleation pathway as well as barriers by performing a series of density functional theory (DFT) calculations. DFT calculations suggested that MAI intercalation allows fluctuation in the lateral dimensions between PbI2 layers, which facilitates nucleation of perovskite nuclei with crystalline orientations complied with recent experiments. By computing perovskite nucleus formation energies with different nucleus sizes, we found that the formation of perovskite nuclei must overcome a nucleation barrier for further growth. The perovskite nucleation barriers are sensitive to both MAI intercalation concentration and perovskite nuclei densities. High MAI intercalation concentration yields high nucleation barriers, and this can be mitigated by forming perovskite films with fine perovskite grains, which is consistent with experimental observations. The present study therefore reveals the atomistic structures of perovskite nuclei embedded in MAI-intercalated PbI2 , and provides insights into the conversion pathway of perovskite from sequential deposition processes. Keywords Perovskite · Two-step process · Nucleation · Density functional theory
Introduction Hybrid organometal halide perovskite materials have drawn a significant amount of attentions in the recent years because of its high optical absorption coefficient around the visible light region [1, 2], tunable band gap energy [3, 4], low exciton binding energy, and long, balanced carrier diffusion lengths [5, 6]. The solar energy conversion efficiencies of photovoltaic cells made from perovskite materials have reached beyond 20% [7, 8], making them one of the promising materials replacing silicon for both lower device fabrication costs as well as weight. In addition to photovoltaic cells, perovskite materials have recently been employed for applications in light-emitting diodes [9], lasers * Chun‑Wei Pao [email protected] 1
Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
Institute for Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
2
[10], photodetectors [11], or photocatalysts [12]. In devices fabricated from perovskite materials such as photovoltaic cells, the device performance critically depends on the morpho
