Effect of PbSO4-Oleate Coverage on Cesium Lead Halide Perovskite Quantum Dots to Control Halide Exchange Kinetics.

Yeonsu Woo,Seeun Park,Seog Joon Yoon

doi:10.3390/nano11102515

Abstract

The selective control of halide ion exchange in metal halide perovskite quantum dots (PQDs) plays an important role in determining their band gap and composition. In this study, CsPbX3 (X = Cl−, Br−, and I−) PQDs were self-assembled with PbSO4-oleate to form a peapod-like morphology to selectively control halide ion exchange. Considering the distinct absorption and bright luminescence characteristics of these PQDs, in situ UV-Vis. absorption and fluorescence spectroscopies were employed to monitor the time-dependent band gap and compositional changes of the PQDs. We determined that the halide exchange in the capped PQDs is hindered—unlike the rapid anion exchange in noncapped PQDs—by a reduction in the halide exchange kinetic rate depending on the extent of coverage of the PQDs. Thus, we tracked the halide ion exchange kinetics between CsPbBr3 and CsPbI3 PQDs, depending on the coverage, using in situ UV-Vis. absorption/photoluminescence spectroscopy. We regulated the halide exchange reaction rate by varying the capping reaction temperature of the PQDs. The capping hindered the halide exchange kinetics and increased the activation energy. These results will enable the development of white LEDs, photovoltaic cells, and photocatalysts with alternative structural designs based on the divalent composition of CsPbX3 PQDs.

Highlights

All-inorganic cesium lead halide (CsPbX3, X: Cl, Br, or I) perovskite quantum dots (PQDs) have emerged as actively studied materials owing to their distinct photophysical properties such as high photoluminescence quantum yields (PLQYs, >90%) [1], dominant radiative recombination processes [1,2,3] and band gap tunability [4,5]
We confirmed that capping significantly increases the activation energy of the halide exchange kinetics
Following the experimental procedure reported by Kamat et al [18,19] we proceeded with the postsynthetic PbSO4 oleate coverage procedure following the synthesis of the CsPbBr3 /CsPbI3 PQDs through a hot-injection process

Summary

Introduction

All-inorganic cesium lead halide (CsPbX3 , X: Cl, Br, or I) perovskite quantum dots (PQDs) have emerged as actively studied materials owing to their distinct photophysical properties such as high photoluminescence quantum yields (PLQYs, >90%) [1], dominant radiative recombination processes [1,2,3] and band gap tunability [4,5]. These outstanding properties have promoted the application of PQDs in various optoelectronic devices and applications such as lasing [6], nonlinear optics [7], light-emitting diodes [4], solar cells [8], and solar-driven chemistry-based devices [1]. This is because halide migration in the perovskite crystalline domain and thermodynamically favorable mixing processes occur

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Results

Conclusion