Energy vs Charge Transfer in Manganese-Doped Lead Halide Perovskites

Abstract

Mn-doped lead halide perovskites exhibit long-lived dopant luminescence and enhanced host excitonic quantum yield. The contention between energy and charge transfer in sensitizing dopant luminescence in Mn-doped perovskites is investigated by state-of-the-art DFT calculations on APbX 3 perovskites (X = Cl, Br, and I). We quantitatively simulate the electronic structure of Mn-doped perovskites in various charge and spin states, providing a structural/mechanistic analysis of Mn sensitization as a function of the perovskite composition. Our analysis supports both energy- and charge-transfer mechanisms, with the latter probably preferred in Mn:CsPbCl 3 due to small energy barriers and avoidance of spin and orbital restrictions. An essential factor determining the dopant luminescence quantum yield in the case of charge transfer is the energetics of intermediate oxidized species, while bandgap resonance can well explain energy transfer. Both aspects are mediated by perovskite host band edge energetics, which is tuned in turn by the nature of the halide X.

Mn‐Doped Perovskite Nanocrystals for Photocatalytic CO2 Reduction: Insight into the Role of the Charge Carriers with Prolonged Lifetime

“…The photogenerated charge carriers in the Mn:CsPbCl 3 NCs have four elementary transfer routes: 1) At CB and valence band (VB) edges, the photogenerated electrons and holes undergo ns time scale recombination, meanwhile, the exciton energy of host transfer to Mn d-states and induce an exciton at Mn from 6 A 1 -4 T 1 (generally on the ps time scale). [43,53] 2) Charge recombination process of the Mn dopants from 4 T 1 -6 A 1 state, which displays ms scale lifetime and is a few orders magnitude longer than the host exciton. 3) Back transfer of electrons from the 4 T 1 state to the CB of the host.…”

“…[ 32 ] This means that the originally short‐lived photogenerated charge carriers can be reserved at Mn 2+ dopants and exist for a significantly longer time. [ 43 ] Therefore, the reserved charge carriers at Mn 2+ dopants can in principle be readily extracted and utilized for surface reaction with less consumption by the fast charge recombination. [ 44 ] In addition, Kamat et al have reported that the midgap states created by Mn 2+ dopants can serve as the electron transfer mediator between CdS/CdSe and TiO 2 , [ 45 ] revealing that the charge carriers at Mn 2+ dopants can be extracted from the inside of the NCs.…”

Time-Resolved Photoluminescence Study of MnS/ZnS Core/Shell Quantum Dots at High Pressure and Low Temperature

“…Historically, there has been some problems and controversies about Mn 2+ emission, including the origin of the Mn emission, the energy level alignment, − and the origin of the ns-scale lifetime component. − Although many efforts and achievements have been made, there are still some difficulties. The energy/charge transfer processes from the host to Mn 2+ ions have attracted wide concern and enormous studies, while they are not completely known yet. − …”

Tuning Excited-State Energy Transfer for Light Energy Conversion: A Virtual Issue

“…The CT mechanism dominates in Mn:CsPbCl 3 as a result of small energy barriers. 7 The surface-functionalized NCs of CsPbBr 3 are also reported to exhibit long-lived delayed luminescence. 8 The TET from the NCs to the phenanthrene ligands and the subsequent thermally activated reverse TET cause the emission from the CsPbBr 3 NCs to be delayed and long-lived.…”

“…The enhanced dopant luminescence lifetime observed in Mn-doped lead halide perovskites (CsPbX 3 : X = Cl, Br, I) has been attributed to an interplay between the charge-transfer and energy-transfer mechanisms, depending on the energy barriers. The CT mechanism dominates in Mn:CsPbCl 3 as a result of small energy barriers . The surface-functionalized NCs of CsPbBr 3 are also reported to exhibit long-lived delayed luminescence …”