Nanoconfined Crystallization of MAPbI3 to Probe Crystal Evolution and Stability
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- 作者：Sangchul Lee ; Joshua Feldman ; Stephanie S. Lee
- 刊名：Crystal Growth & Design
- 出版年：2016
- 出版时间：August 3, 2016
- 年：2016
- 卷：16
- 期：8
- 页码：4744-4751
- 全文大小：489K
- 年卷期：0
- ISSN：1528-7505
文摘
The effect of nanoconfinement on the crystallization of methylammonium lead iodide (MAPbI3) was systematically studied using two-dimensional X-ray diffraction (2D XRD). Nanoconfined crystals were prepared by spin coating a cosolution of lead iodide (PbI2) and methylammonium iodide (MAI) dissolved in N,N-dimethylformamide or dimethyl sulfoxide onto anodized aluminum oxide (AAO) templates with uniaxially aligned pores ranging from 20–200 nm in diameter. Upon spin coating, a metastable crystalline phase incorporating solvent molecules was observed. Analysis of 2D XRD patterns using refined lattice parameters revealed that these crystals adopt a preferential orientation with alternating sheets of PbI2 and solvent molecules lying parallel to the long axis of the pores. Upon thermal annealing at temperatures up to 130 °C, the oriented PbI2/solvent crystals converted to randomly oriented MAPbI3 crystals, with the extent of conversion dependent on the characteristic pore diameter of the AAO template. Nanoconfinement was further observed to affect the stability of MAPbI3 crystals exposed to air. Unconfined MAPbI3 crystals degraded to PbI2 within a period of 2 weeks of air exposure, accompanied by a significant change in crystal morphology. In contrast, MAPbI3 crystals confined in AAO templates with a characteristic pore size of 100 nm were stable over the same period.