Volume 56, Issue 15 pp. 4160-4164
Communication

Composition-Dependent Hot Carrier Relaxation Dynamics in Cesium Lead Halide (CsPbX3, X=Br and I) Perovskite Nanocrystals

Heejae Chung

Heejae Chung

Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722 Republic of Korea

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Seok Il Jung

Seok Il Jung

Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722 Republic of Korea

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Hyo Jin Kim

Hyo Jin Kim

Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722 Republic of Korea

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Wonhee Cha

Wonhee Cha

Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722 Republic of Korea

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Prof. Dr. Eunji Sim

Prof. Dr. Eunji Sim

Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722 Republic of Korea

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Prof. Dr. Dongho Kim

Prof. Dr. Dongho Kim

Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722 Republic of Korea

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Dr. Weon-Kyu Koh

Corresponding Author

Dr. Weon-Kyu Koh

Device Laboratory, Samsung Advanced Institute of Technology, Suwon, Gyeonggi-do, 16676 Republic of Korea

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Prof. Dr. Jiwon Kim

Corresponding Author

Prof. Dr. Jiwon Kim

School of Integrated Technology and Underwood International College, Yonsei University, Incheon, 21983 Republic of Korea

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First published: 20 March 2017
Citations: 157

Graphical Abstract

Significant dependence of the hot-carrier relaxation rate on the halide (Br, I, or their mixture) is mainly attributable to the density of states for holes in the valence band of CsPbX3 nanocrystals. The hot-carrier relaxation rate is observed to decrease from CsPbBr3 to CsPbI3 NC. VB=valence band, CB=conduction band.

Abstract

Cesium-based perovskite nanocrystals (NCs) have outstanding photophysical properties improving the performances of lighting devices. Fundamental studies on excitonic properties and hot-carrier dynamics in perovskite NCs further suggest that these materials show higher efficiencies compared to the bulk form of perovskites. However, the relaxation rates and pathways of hot-carriers are still being elucidated. By using ultrafast transient spectroscopy and calculating electronic band structures, we investigated the dependence of halide in Cs-based perovskite (CsPbX3 with X=Br, I, or their mixtures) NCs on the hot-carrier relaxation processes. All samples exhibit ultrafast (<0.6 ps) hot-carrier relaxation dynamics with following order: CsPbBr3 (310 fs)>CsPbBr1.5I1.5 (380 fs)>CsPbI3 NC (580 fs). These result accounts for a reduced light emission efficiency of CsPbI3 NC compared to CsPbBr3 NC.

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