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Impact of the Solvation State of Lead Iodide on Its Two‐Step Conversion to MAPbI 3 : An In Situ Investigation
Author(s) -
Barrit Dounya,
Cheng Peirui,
Tang MingChun,
Wang Kai,
Dang Hoang,
Smilgies DetlefM.,
Liu Shengzhong Frank,
Anthopoulos Thomas D.,
Zhao Kui,
Amassian Aram
Publication year - 2019
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201807544
Subject(s) - materials science , energy conversion efficiency , iodide , chemical engineering , solar cell , annealing (glass) , perovskite (structure) , absorbance , solvation , inorganic chemistry , optoelectronics , solvent , optics , organic chemistry , chemistry , composite material , engineering , physics
Producing high efficiency solar cells without high‐temperature processing or use of additives still remains a challenge with the two‐step process. Here, the solution processing of MAPbI 3 from PbI 2 films in N , N ‐dimethylformamide (DMF) is investigated. In‐situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) measurements reveal a sol–gel process involving three PbI 2 ‐DMF solvate complexes—disordered (P 0 ) and ordered (P 1 , P 2 )—prior to PbI 2 formation. When the appropriate solvated state of PbI 2 is exposed to MAI (methylammonium Iodide), it can lead to rapid and complete room temperature conversion into MAPbI 3 with higher quality films and improved solar cell performance. Complementary in‐situ optical reflectance, absorbance, and quartz crystal microbalance with dissipation (QCM‐D) measurements show that dry PbI 2 can take up only one third of the MAI taken up by the solvated‐crystalline P 2 phase of PbI 2 , requiring additional annealing and yet still underperforming. The perovskite solar cells fabricated from the ordered P 2 precursor show higher power conversion efficiency (PCE) and reproducibility than devices fabricated from other cases. The average PCE of the solar cells is greatly improved from 13.2(±0.53)% (from annealed PbI 2 ) to 15.7(±0.35)% (from P 2 ) reaching up to 16.2%. This work demonstrates the importance of controlling the solvation of PbI 2 as an effective strategy for the growth of high‐quality perovskite films and their application in high efficiency and reproducible solar cells.