Direct Correlation of Charge Carrier Transport to Local Crystal Quality in Lead Halide Perovskites

Abstract

Although solution processing methods provide an attractive route toward development of low-cost functional materials, these accessible fabrication approaches can engender high concentrations of microscopic structural defects that are detrimental to performance. In lead halide perovskites, structural disorder derived from solution processing has been implicated as an important determiner of photophysical properties. However, a direct correlation between the functional properties of these materials and the local crystal structure in which non-equilibrium states evolve has remained elusive, in part because structural heterogeneities occur on length scales that defy conventional characterization techniques. To address this knowledge gap, we have combined ultrafast pump–probe microscopy and electron backscattering diffraction to directly correlate charge carrier transport with the local diffraction pattern contrast, an indicator of crystal quality. Spatial correlation of these measurements strongly suggests that even on individual single crystal CsPbBr3 domains, microscopic variability in the crystal quality profoundly impacts the efficiency of charge carrier transport.

Atomistic origin of lattice softness and its impact on structural and carrier dynamics in three dimensional perovskites

“…67 However, the explicit origins of dynamic disorder remain debated. Postulated origins include the rotation of organic cations, 68,69 solution processing, 70 high polarizability of Pb and its lessdirectional bonding than transition metals, 13 and presence of lone-pair s electrons. 71 In this work, we attempted to clarify the origins of dynamic disorder by carrying out Born-Oppenheimer MD simulations at 300 K for b-MAPbI In order to quantitatively characterize the dynamic disorder, the average standard deviation (s) for the positions of Pb and I atoms in MD trajectories was calculated using the following equation: 72,73 s ¼…”

Interfaces and Interfacial Carrier Dynamics in Perovskites

“…Grumstrup and co-workers reported the local carrier transport within a single crystal CsPbBr3 domain by using transient reflection microscopy. They found that the diffusion coefficient could be reduced by nearly an order of magnitude in the same grain, which indicate that the local crystal quality in the grain interior profoundly impacts the efficiency of charge carrier transport . By using transient photoluminescence microscopy and Kelvin probe force microscopy (KPFM) measurements, Tisdale et al.…”

“…They found that the diffusion coefficient could be reduced by nearly an order of magnitude in the same grain, which indicate that the local crystal quality in the grain interior profoundly impacts the efficiency of charge carrier transport. 58 By using transient photoluminescence microscopy and Kelvin probe force microscopy (KPFM) measurements, Tisdale et al investigated the difference between carrier diffusion in perovskite single crystals and polycrystalline thin films. Their results show that carrier diffusivity in MHP single crystals is independent of composition.…”

Elucidation of Quantum-Well-Specific Carrier Mobilities in Layered Perovskites

“…The magnitude of the excited-state emission-like nonlinearity can be simulated by replacing σ abs (ω 2 ) with the emission rate σ em (ω 2 )­ Similarly, an excited-state absorption-like term can be obtained by replacing σ em (ω 2 ) with the rate of light absorption between singly and doubly excited states. Based on previous transient absorption microscopy results for these systems, our formulas are written under the assumption that the drift velocity is primarily governed by extrinsic properties of the material (e.g., traps, disorder, grain boundaries) rather than the natures of the quantum states. ,, …”

“…Based on previous transient absorption microscopy results for these systems, our formulas are written under the assumption that the drift velocity is primarily governed by extrinsic properties of the material (e.g., traps, disorder, grain boundaries) rather than the natures of the quantum states. 6,46,47 The delay-dependent electron and hole densities, which govern the nonlinear photocurrent J(τ,t), may be simulated with knowledge of the mobilities, two-body recombination coefficients, and trap-induced broadening of the carrier distributions (see Supporting Information). The two-body recombination coefficient of 3.3 × 10 −9 cm 3 /s was obtained in earlier experimental work, 6,46 whereas we have set the mobility equal to 0.015 cm 2 /V/s based on the shapes of the NLPC decay curves observed in the experiments below.…”