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The Impact of a Dynamic Two‐Step Solution Process on Film Formation of Cs 0.15 (MA 0.7 FA 0.3 ) 0.85 PbI 3 Perovskite and Solar Cell Performance
Author(s) -
Bing Jueming,
Kim Jincheol,
Zhang Meng,
Zheng Jianghui,
Lee Da Seul,
Cho Yongyoon,
Deng Xiaofan,
Lau Cho Fai Jonathan,
Li Yong,
Green Martin A.,
Huang Shujuan,
HoBaillie Anita W. Y.
Publication year - 2019
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201804858
Subject(s) - materials science , formamidinium , spin coating , iodide , annealing (glass) , perovskite (structure) , nucleation , chemical engineering , solution process , thin film , nanotechnology , inorganic chemistry , chemistry , optoelectronics , organic chemistry , composite material , engineering
This paper provides deep understanding of the formation mechanism of perovskite film fabricated by sequential solution‐based methods. It compares two sequential spin‐coating methods for Cs 0.15 (MA 0.7 FA 0.3 ) 0.85 PbI 3 perovskite. First is the “static process,” with a stoppage between the two spin‐coating steps (1st PbI 2 ‐CsI‐dimethyl sulfoxide (DMSO)‐dimethylformamide (DMF) and 2nd methylammonium iodide (MAI)‐formamidinium iodide (FAI)‐isopropyl alcohol). Second is the “dynamic process,” where the 2nd precursor is dispensed while the substrate is still spinning from the 1st step. For the first time, such a dynamic process is used for Cs 0.15 (MA 0.7 FA 0.3 ) 0.85 PbI 3 perovskite. Characterizations reveal improved film formation with the dynamic process due to the “retainment” of DMSO‐complex necessary for the intermediate phase which i) promotes intercalation between precursors and ii) slows down perovskite crystallization for full conversion. The comparison on as‐deposited perovskite before annealing indicates a more ordered film using this dynamic process. This results in a thicker, more uniform film with higher degree of preferred crystal orientation and higher carrier lifetime after annealing. Therefore, dynamic‐processed devices present better performance repeatability, achieving a higher average efficiency of 17.0% compared to static ones (15.0%). The new insights provided by this work are important for perovskite solar cells processed sequentially as the process has greater flexibility in resolving solvent incompatibility, allowing separate optimizations and allowing different deposition methods.