CsPbBr₃ Nanocrystal/MO₂ (M = Si, Ti, Sn) Composites: Insight into Charge-Carrier Dynamics and Photoelectrochemical Applications

Abstract

Though coating CsPbBr3 nanocrystal (NC) with an outer layer has been regarded as an effective strategy to address its instability issues, deep investigations into the electronic interaction between CsPbBr3 NC and coating layer have yet to be conducted. In this study, the dynamics of hot carrier and charge carrier of CsPbBr3 nanocrystal with various MO2 (M = Si, Ti, Sn) coating layers have been comprehensively studied. Combined transient optical characterizations (time-resolved photoluminescence and ultrafast transient absorption) and photoelectrochemical measurements reveal that coating with insulating SiO2 accelerates the hot carrier relaxation and enhances the radiative recombination by passivating surface traps, whereas efficient charge-carrier separation and extraction are observed after coating with SnO2 and TiO2. The electron injection from CsPbBr3 NC to SnO2 (1.14 × 108 s–1) is 2-fold faster than to TiO2 (5.4 × 107 s–1) owing to the lower conduction band edge and the higher electron mobility of SnO2. Particularly, the first time fabricated CsPbBr3 NC/SnO2 composite exhibits superior stability against UV light and moisture, as well as the best photocurrent response in this study. This work has implied that rational design of the coating layer for perovskite NC can not only improve the stability but also tailor the electronic and optoelectronic properties for various applications.

Influence of the rate of radiation energy on the charge-carrier kinetics application of all-inorganic CsPbBr3 perovskite nanocrystals

“…1b 30 and the emission peak was seen at 516 nm, derived from the photoluminescence (PL) emission spectrum, as depicted in Fig. 1c, 30 and PLQY was calculated to be 38.7%, as listed in Table S1. †…”

“…The TRPL spectroscopy was further carried out in order to get further insight into the carrier kinetics in a quantitative way. 30,[48][49][50] Using tri-exponential functions, 22 the PL tted the decay curve pictured in Fig. 1d, and the computed values are listed in Table S2.…”

“…The TA spectroscopy was used to overcome the time resolution limitations of the TRPL technique to probe into the hot carrier kinetics. 30 The fundamental physical processes of TA have three contributions namely (i) ground state bleach (GSB), (ii) stimulated emission (SE), and (iii) photo-induced absorption (PIA). In order to produce a TA spectrum, the probe pulse is transmitted through the sample at several time delays concerning with or without the pump pulse.…”

“…2d represents the intraband state of the surface trap of PNC. 30,35,37 The DA intensity of the GSB signal helps to evaluate the carrier density in terms of the bandgap. 35,37,63 Fig.…”

“…44 With the variation in the halide composition from CsPbBr 3 to CsPbI 3 , Kim et al reported a comparative study of hot carrier cooling. 45 The pump uence-based study of the mechanism behind hot carrier cooling in MAPbI 3 NCs was reported by Fu et al 46 The intensity-dependent investigation of the hot carrier cooling process in CsPbI 3 quantum dots was examined by Feng Liu et al 47 Similarly, the wavelengthdependent mechanism of the hot-carrier cooling phenomenon in CsPbBr 3 NC/MO 2 (M ¼ Si, Ti, and Sn) composites was investigated by Kuang et al 30 Herein, all-inclusive chargecarrier kinetics was looked into the CsPbBr 3 PNCs using the TRPL and the rate of radiation energy-dependent TA spectroscopy. To the best of our knowledge, we have also reported the kinetic Burstein-Moss shi attribute of the band edge carrier aggregation in the CsPbBr 3 PNC material in the context of the rate of radiation dependence.…”