Unraveling the Crystallization Kinetics of 2D Perovskites with Sandwich‐Type Structure for High‐Performance Photovoltaics

• Published in: Advanced materials (Weinheim) Vol. 32; no. 36; pp. e2002784 - n/a
• Main Authors: Song, Jingnan, Zhou, Guanqing, Chen, Wei, Zhang, Quanzeng, Ali, Jazib, Hu, Qin, Wang, Jing, Wang, Cheng, Feng, Wei, Djurišić, Aleksandra B., Zhu, Haiming, Zhang, Yongming, Russell, Thomas, Liu, Feng
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.09.2020; Wiley Blackwell (John Wiley & Sons)
• Subjects: 2D perovskites; Absorption spectra; Alkali metals; Cations; Coalescing; Crystal defects; Crystallization; crystallization kinetics; in situ GIWAXS; Kinetics; Morphology; Perovskites; Photovoltaic cells; Recrystallization; sandwich‐type structures; Solar cells; Solvents; Surface defects; Tolerances
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202002784

2D perovskite solar cells with high stability and high efficiency have attracted significant attention. A systematical static and dynamic structure investigation is carried out to show the details of 2D morphology evolution. A dual additive approach is used, where the synergy between an alkali metal cation and a polar solvent leads to high‐quality 2D perovskite films with sandwich‐type structures and vertical phase segregation. Such novel structure can induce high‐quality 2D slab growth and reduce internal and surface defects, resulting in a high device efficiency of 16.48% with enhanced continuous illumination stability and improved moisture (55–60%) and thermal (85 °C) tolerances. Transient absorption spectra reveal the carrier migration from low n to high n species with different kinetics. An [PbI6]4− octagon coalescence transformation mechanism coupled with metal and organic cations wrapped is proposed. By solvent vapor annealing, a recrystallization and reorientation of the 2D perovskite slabs occurs to form an ideal structure with improved device performance and stability. An in situ grazing‐incidence wide‐angle X‐ray scattering experiment is conducted to reveal the crystallization kinetics and formation mechanism of 2D perovskite films, during which additives play a key role in regulating the nucleation and growth process. For the dual additive processing case, a novel sandwich‐type structure is achieved, which can effectively passivate defects at dual interfaces, finally resulting in a high device efficiency of 16.48%.