Enhanced stability and optical properties of Gd3+ doped CsPbI3 nanocrystals

M. Yenal Yalcinkaya^a, C. Meric Guvenc^a, Sercan Ozen^b, Hasan Sahin^b, Mustafa M. Demir^a

^aDepartment of Materials Science and Engineering, Izmir Institute of Technology, Turkey, Izmir, Turkey

^bDepartment of Photonics, Izmir Institute of Technology, Turkey, Izmir, Turkey

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#NCFun19. Fundamental Processes in Semiconductor Nanocrystals

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Ivan Infante and Jonathan Owen

Oral, M. Yenal Yalcinkaya, presentation 134
DOI: https://doi.org/10.29363/nanoge.nfm.2019.134
Publication date: 18th July 2019

ABSTRACT

All inorganic CsPbI₃ perovskites are considered as alternatives to hybrid perovskite structures such as MAPbI₃ and FAPbI₃ due to their better stability. Despite their high potential for optoelectronic applications, they still suffer from stability under ambient conditions. CsPbI₃ perovskites usually present in two phases: high temperature α-CsPbI₃ phase and low temperature δ-CsPbI₃ phase. The α-CsPbI₃ phase is suitable for optoelectronic applications due to its 1.73 eV band gap. However, α-CsPbI₃ phase is not thermodynamically stable at temperatures below 320 °C and transforms to non-perovskite δ-CsPbI₃ phase which is not suitable for optoelectronic applications due to its high band gap of 2.26 eV. In order to utilize CsPbI₃ perovskites in optoelectronic applications, the stability issue of α-CsPbI₃ phase must be solved. In this study, Gd³⁺ ion was doped into the CsPbI₃ perovskite structure to increase stability of the α-CsPbI₃ phase in ambient conditions. Doped CsPbI₃ nanocrystals (NCs) completely transformed to δ-CsPbI₃ phase in 11 days, while undoped CsPbI₃ NCs completely transformed to δ-CsPbI₃ in 5 days. This prolonged phase stability can be originated from three potential reasons: increased Goldschmidt's tolerance factor, distorted cubic symmetry, and reduced defect density. Urbach energies of the samples suggest reduced defect density in the perovskite NCs. Furthermore, by doping α-CsPbI₃ NCs with 10% moles Gd³⁺ ions, photoluminescence quantum yield (PLQY) is increased from 70% to 80% and flourescence lifetime of α-CsPbI3 is increased from 47.4 ns to 64.4 ns. Also, density functional theory (DFT) calculations are consistent with the experimental results.

References:

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