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Evidence for polarization-induced phase transformations and degradation in CH3NH3PbI3.
- Source :
- Nano Research; Jul2023, Vol. 16 Issue 7, p9435-9442, 8p
- Publication Year :
- 2023
-
Abstract
- In solar cells, hybrid halide perovskites operate under constant bias, thus their stability towards electric field-induced degradation is of key importance. Here we report on evidence of previously unidentified electric field-induced transitions and degradation path of CH<subscript>3</subscript>NH<subscript>3</subscript>PbI<subscript>3</subscript> (MAPbI<subscript>3</subscript>) using elemental and phase mapping. Thin films of MAPbI<subscript>3</subscript> were deposited onto 1–2 µm-pitch interdigitated electrodes and subjected to direct current (DC)-polarization. The MAPbI<subscript>3</subscript> layer polarized with < 0.8 V/µm DC electric field undergoes pronounced ion redistribution to methylammonium-rich MAPbI<subscript>3−y</subscript> (y < 0.6) and iodine-rich MA<subscript>1−x</subscript>PbI<subscript>3</subscript> (x < 0.3) regions. Polarization-induced loss of both methylammonium and iodine provokes degradation of MAPbI<subscript>3</subscript>. Using nanofocus grazing-incidence wide-angle X-ray scattering (GIWAXS), we unambiguously showed that the bias voltage induces the transformation of β-MAPbI<subscript>3</subscript> to metastable δ-MAPbI<subscript>3</subscript> polymorph via alignment of polar organic cation with the electric field. This transformation is partially reversible upon field removal. However, once formed, δ-MAPbI<subscript>3</subscript> disrupts the morphology of pristine film and undergoes decomposition to β-MAPbI<subscript>3</subscript> (β-MAPI) and PbI<subscript>2</subscript>. With the aforementioned compositional and phase changes, only MA-rich part serves as the charge separation layer, while the I-rich excitation is blocked with the PbI<subscript>2</subscript> barrier serving as holes trapping layer. These observations reveal the intermediate steps in electric-field-driven degradation of halide perovskites and show the role of polar cations in the process, which is instructive for further material design with higher stability metrics. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 19980124
- Volume :
- 16
- Issue :
- 7
- Database :
- Complementary Index
- Journal :
- Nano Research
- Publication Type :
- Academic Journal
- Accession number :
- 169750774
- Full Text :
- https://doi.org/10.1007/s12274-023-5652-8