Complete ultrafast charge carrier dynamics in photo-excited all-inorganic perovskite nanocrystals (CsPbX₃)

Abstract

Understanding the nature and dynamics of the photo-induced transients of all-inorganic perovskite nanocrystals (NCs) is key to their exploitation in potential applications. In order to determine the nature of charge carriers, their deactivation pathways and dynamics, the photo-induced transients of CsPbBr, CsPbBrI, CsPbBrI and CsPbI NCs are spectrally and temporally characterized employing a combination of femtosecond transient absorption (TA) and photoluminescence (PL) up-conversion techniques and global analysis of the data. The results provide distinct identities of the excitons and free charge carriers and distinguish the hot charge carriers from the cold ones. The carrier trapping is attributed to the electrons and their dynamics is unaffected in mixed halide perovskites. The excitation energy dependence of the TA dynamics suggests that the trap states are shallow in nature and mainly limited near the band-edge level. In mixed halide perovskites, an increase in the iodine content leads to hole trapping in a short time scale (<5 ps). The insights obtained from this study are likely to be helpful for tuning the photo-response of these substances and their better utilization in light-based applications.

Single Halide Perovskite/Semiconductor Core/Shell Quantum Dots with Ultrastability and Nonblinking Properties

“…Point angle of the cubic shape become circular arc, which further suggests the formation of CdS shell (Figure 1d). [31][32][33] The surface compositions of the CsPbBr 3 /CdS QDs were characterized by X-ray photo electron spectroscopy (XPS) analysis. No distinct lattice pattern of CdS layer has been observed, which is probably due to the thinness of the layer and the background noise.…”

Metal halide perovskite nanocrystals and their applications in optoelectronic devices

“…PB2 recovers rapidly, causing the spectral envelope of PA1 to broaden. The formation of PB1 is represented by ultrafast (<120 fs) and relatively slow (~700 fs) components, while PB2 and PA2 are characterized by a limited rise time of the instrument (≤120 fs) . PB1 is attributed to a decrease in the ground state because its peak position matches the first exciton absorption peak of CsPbBr 3 .…”

“…C. TA spectra of CsPbBr 3 NCs ( λ ex = 350 nm) at different delay times (50 fs to 2000 ps) highlighting formation and decay of various TA signals. Reproduced with permission . Copyright 2017 Royal Society of Chemistry.…”

“…72,73 The application of ultrafast pump-probe spectroscopy has revealed many important features of the photogenerated transients of perovskite NCs, such as long electron-hole diffusion length, high charge carrier mobility, low exciton beam binding energy. 74,75 The photoexcitation of a given semiconductor NCs, characterized by the absorption and PL spectra are shown in Figure 3B, can initiate various pump-induced processes and produce typical transient absorption (TA) spectra, as shown in Figure 3A,B. We take CsPbBr 3 NCs for some discussion ( Figure 3C).…”

Ultraviolet Photodetectors Based on CH3NH3PbCl3 Perovskite Quantum Dots‐Doped Poly(triarylamine)

“…Metal halide perovskite nanocrystals have attracted tremendous research interests and have been widely used in many high‐performance optoelectronic devices, such as lasers, solar cells, light‐emitting diodes (LEDs), and photodetectors in the past few years. In particular, the exceptional optoelectronic properties, including long electron–hole diffusion length, long carrier lifetime, high absorption coefficient, and large carrier mobility, offer tremendous space to enhance the device performance . In this work, we incorporate CH 3 NH 3 PbCl 3 perovskite quantum dots (QDs) into a thick PTAA active layer and try to enhance the charge transport and device performance.…”