Efficient Exciton Dissociation through the Edge Interfacial State in Metal Halide Perovskite-Based Photocatalysts

Abstract

Metal halide perovskites (MHPs) with superior optoelectronic properties have recently been actively pursued as catalysts in heterogeneous photocatalysis. Dissociating excitons into charge carriers holds the key to enhancing the photocatalytic performance of MHP-based photocatalysts, especially for those with strong quantum-confinement effects. However, attaining efficient exciton dissociation has been rather challenging. Herein, we propose a novel concept that the edge interfacial state can trigger anisotropic electron transfer to promote exciton dissociation. By taking Cs4PbBr6/TiO2 mesocrystal heterojunction as a proof-of-concept, we demonstrate that the unique interfacial state at the edge of the system is generated by the defect-mediated chemical interaction and acts as a trap state, which brings on a directionally favored electron transfer from the center to edge regions, thereby significantly enhancing the desired exciton dissociation. Consequently, such a system achieves an excellent performance in photocatalytic CO2 reduction. This paradigmatic work sheds light on the excitonic aspects for rational design of advanced photocatalysts toward high performance.

Fermi-level shift, electron separation, and plasmon resonance change in Ag nanoparticle-decorated TiO2 under UV light illumination

“…The method used to study the E F and electron storage is not limited to Ag nanoparticles and TiO 2 , which can be used for the other metallic nanoparticle-decorated semiconductors. In addition, heterojunction photocatalysis was also studied to increase the photocatalytic activities by separating charge carriers, for example, the recently studied lead-free bismuth halide perovskite nanocrystals encapsulated in a covalent organic framework, 36 Cs 4 PbBr 6 / TiO 2 37 and BiVO 4 /TiO 2 . 38 In principle, the method developed in the current research can be also used to study the electron separation and storage in heterojunction structures.…”

Charge Trapping in Semiconductor Photocatalysts: A Time- and Space-Domain Perspective

“…Inspired by the findings in Figure , we have deliberately introduced oxygen vacancies at the edge of TiO 2 mesocrystal (TMC) and hybridized it with Cs 4 PbBr 6 (CPB) . From fs-TAS measurements (Figure a,b), it is found that the interfacial electron transfer rate constant of the optimized CPB/TMC heterojunction is much larger than those reported in the literature, suggesting a new exciton-dissociation mechanism where the anisotropic electron transfer occurs.…”

“…(e) Schematic illustration of the IFS-triggered anisotropic electron transfer for efficient exciton dissociation in CPB/TMC. Adapted with permission from ref . Copyright 2023 American Chemical Society.…”

Promoting Photocatalytic H2 Evolution through Retarded Charge Trapping and Recombination by Continuously Distributed Defects in Methylammonium Lead Iodide Perovskite

“…The triexponential fitting yields the relaxation time constants (and weighted coefficients): τ 1 = 20 � 2 ps (33 %), τ 2 = 140 � 10 ps (40 %), τ 3 = 1300 � 200 ps (20 %), and a constant of τ 0 @ 8 ns (7 %) for MAPbI 3 -I. As the charge trapping usually occurs on a timescale of picosecond [31,32] and the radiative recombination of MAPbI 3 is found to occur on the timescale of several to tens of nanoseconds (Figure S15), we can safely attribute the relaxation time constants to the events of electron trapping at defect states with different depths (τ 1 and τ 2 ), nonradiative recombination (τ 3 ), and radiative recombination (τ 0 ), as illustrated in Scheme 2a. Obviously, the GSB relaxation dynamics for MAPbI 3 -C gets retarded with longer lifetimes of τ 1 = 41 � 5 ps (27 %), τ 2 = 220 � 30 ps (37 %), τ 3 = 2200 � 300 ps (28 %), and τ 0 @ 8 ns (8 %), as illustrated in Scheme 2b.…”