Insights about air induced structural changes in perovskite thin films using transmission electron microscopy and optical measurements
Romika Sharma a, Qiannan Zhang b, Linh Lan Nguyen a, Tze Chien Sum b, Martial Duchamp a, Yeng Ming Lam a
a School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Technological University, Singapore 639798, Singapore
b School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371 Singapore
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP23)
Kobe, Japan, 2023 January 22nd - 24th
Organizers: Seigo Ito, Hideo Ohkita and Atsushi Wakamiya
Oral, Romika Sharma, presentation 013
Publication date: 21st November 2022

The advantages of organic-inorganic halide perovskites, such as their configurable bandgap, inexpensive material costs, and high charge carrier mobilities, make them intriguing -candidates for next-generation solar cell and opto-electronic applications. Despite tremendous advancements, worries regarding material stability still prevent the widespread use of perovskite-based technology. Using transmission electron microscopy (TEM) and time-resolved photoluminescence (TRPL) techniques, we investigate how environmental factors impact the structural and optical characteristics of thin film perovskites.

The hydrophilic nature of 3D halide perovskites renders them sensitive to temperature and moisture. As a result, the organic cation of 3D halide perovskite can be easily destroyed in an ambient environment. But the stability of 3D halide perovskites can be improved by decreasing the perovskite dimensionality. To create lower dimension perovskites, large organic cations such as phenyl-ethyl ammonium (PEA) are added to the 3D perovskites.

In this work, we compare the stability of 3D perovskite, MAPbI3 (CH3NH3PbI3) and 2D perovskites, (PEA)2PbBr4 against environmental conditions like moisture and air. The characterizations are performed on perovskite thin films exposed to air, nitrogen and vacuum environments, the latter being possible by using dedicated air-free transfer setups, after their fabrication into a nitrogen-filled glovebox. We observe that even less than three minutes air-exposure increases the sensitivity to electron beam deterioration and modifies the structural transformation pathway for 3D MAPbI3 thin films.

However, in comparison to their 3D counterparts, 2D perovskite films show better stability. Their distinct layered structural layout makes it possible to adjust their physical and chemical properties using organic spacer cations.

The findings pave the way to understand the relationship between the microstructural changes and the optical properties of perovskites when subjected to air-induced degradation.

Financial support from Nanyang Technological University and the Ministry of Education Tier 2 grant MOE2019-T2-2-066; is gratefully acknowledged. Q.Z. and T.C.S. also acknowledge the support from the AcRF Tier 2 grant MOE2019-T2-1-006.

We would like to acknowledge the Facility for Analysis, Characterisation, Testing and Simulation, Nanyang Technological University, Singapore, for use of their electron microscopy/X-ray facilities.

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