Exploring the Carrier Dynamics in Zinc Oxide–Metal Halide-Based Perovskite Nanostructures: Toward Reduced Dielectric Loss and Improved Photocurrent

Abstract

Metal halide-based perovskites have emerged as a potential candidate for optoelectronic applications because of their impressive performance achieved by tuning the optical/electrical properties through tailoring the perovskite nanostructures. Herein, we report the synthesis of composite nanostructures by incorporation of ZnO (∼6 nm) into the CsPbBr 3 (CPB) perovskite framework, which shows significant enhancement of photocurrent because of efficient interfacial charge separation and reduced dielectric loss. Detailed steady-state and time-resolved photoluminescence studies have been carried out to understand charge transfer dynamics in the CsPbBr 3 /ZnO nanostructure composite system. Femtosecond transient absorption and broadband dielectric spectroscopy studies were carried out to determine the charge carrier relaxation and transfer mechanism. The redox energy-level diagram suggests that the photoexcited electron from the conduction band (CB) of CPB can be transferred to the CB of ZnO NP because of thermodynamic viability. Ultrafast studies reveal that the electron transfer takes place from the perovskite nanostructures to ZnO NP within ∼500 fs and limits the recombination process by efficient charge separation and charge accumulation at the interfaces. Dielectric studies also reveal reduced charge leakage in composite nanostructures with efficient charge separation by facilitating the charge accumulation at the interfaces. Overall, the efficient charge transfer and slow carrier recombination with reduced dielectric losses significantly improved the photocurrent behavior in the CsPbBr 3 /ZnO nanostructure composite system as desired for optoelectronic devices.

Ultrafast Charge Delocalization Dynamics of Ambient Stable CsPbBr3 Nanocrystals Encapsulated in Polystyrene Fiber

“…The bleach kinetics of pure CsPbBr 3 (Figure 8 a) can be fitted with bi‐exponential growth with time constants of τ g 1 <100 fs (54 %) and τ g 2 =0.73 ps (46 %) and multi‐exponential decay with time constants of τ 1 =44 ps (−56 %), τ 2 =240 ps (−28 %), and τ 3 >1 ns (−16 %; Table 1). Bi‐exponential growth in the bleach kinetics can be due to the carrier (electron) cooling dynamics from the upper excitonic states to the conduction band edge as we have observed previously [28, 34, 35] . On the other hand, multi‐exponential kinetics can be attributed to the charge recombination dynamics between photoexcited charge carriers of CsPbBr 3 NCs, which closely matches with our previous reports [40, 41] .…”

“…Pure CsPbBr 3 NCs shows a bleach in the 470–560 nm spectral region with a peak at approximately 512 nm, and at an early time a positive absorption band appears at 526 nm. In addition, at longer timescales, a positive absorption band appears at 460–495 nm wavelength region with a peak at approximately 483 nm [34–39] . The transient spectral features match quite well with our previous studies [40, 41] and also those by others [37, 38] .…”

“…The sharp negative absorption change (bleach) around 515 nm can be attributed to the ground state 1S excitonic transition, which matches with the observed steady‐state absorption spectra. The positive absorption band at very early timescale, peaking at 526 nm, can be attributed to the probe‐induced bi‐exciton Stark effect [34–36] . In addition to that, the TA spectra show photoinduced absorption (PA) at 480–500 nm, which could be due to the hot exciton induced absorption [37–39] .…”

Experimental and Theoretical Study into Interface Structure and Band Alignment of the Cu2Zn1–xCdxSnS4 Heterointerface for Photovoltaic Applications

“… 3 , 25 The femtosecond transient absorption spectroscopy was carried out using HELIOS ultrafast setup. 26 …”

MCdCl3 (M=CH3NH3, (CH3)2NH2): New Hybrid Perovskites with Large Dielectric Constants for Field‐Effect Transistors

“…[26,37,39,40] In addition, the rapid diminution in ε 0 versus frequency was mostly on account of the ionic transport and the reduction in effect of space charge polarization. [41,42] However, with the increase in temperature from 303 to 423 K, the values of dielectric constants in both perovskites also rose from % 10 2 to % 10 3 which mainly resulted from the charge accumulation at the grain boundaries, the appearance of thermally activated charge carriers, and the electric dipole moment. [43,44] Based on the literature, Table 3 shows a list of dielectric constants for different materials, including OIHPs, organic, and inorganic semiconductors.…”