title: Heterogeneous Charge Carrier Dynamics in Organic-Inorganic Hybrid Materials: Nanoscale Lateral and Depth-Dependent Variation of Recombination Rates in Methylammonium Lead Halide Perovskite Thin Films.
abstract: We reveal substantial luminescence yield heterogeneity among individual subdiffraction grains of high-performing methylammonium lead halide perovskite films by using high-resolution cathodoluminescence microscopy. Using considerably lower accelerating voltages than is conventional in scanning electron microscopy, we image the electron beam-induced luminescence of the films and statistically characterize the depth-dependent role of defects that promote nonradiative recombination losses. The highest variability in the luminescence intensity is observed at the exposed grain surfaces, which we attribute to surface defects. By probing deeper into the film, it appears that bulk defects are more homogeneously distributed. By identifying the origin and variability of a surface-specific loss mechanism that deleteriously impacts device efficiency, we suggest that producing films homogeneously composed of the highest-luminescence grains found in this study could result in a dramatic improvement of overall device efficiency. We also show that although cathodoluminescence microscopy is generally used only to image inorganic materials it can be a powerful tool to investigate radiative and nonradiative charge carrier recombination on the nanoscale in organic-inorganic hybrid materials.
authors.forename: Connor G
authors.initials: CG
authors.lastname: Bischak
authors.affiliation: ⊥National Renewable Energy Laboratory, Golden, Colorado 80401, United States.|#Department of Electrical Engineering, University of Washington, Seattle, Washington 98195, United States.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Sanehira
authors.forename: Jake T
authors.initials: JT
authors.lastname: Precht
authors.affiliation: ⊥National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Luther
authors.affiliation: ∇Kavli Energy NanoSciences Institute, Berkeley, California 94720, United States.
authors.forename: Naomi S
authors.initials: NS
authors.lastname: Ginsberg
keywords: Methylammonium-lead halide perovskite; cathodoluminescence; nanoimaging; nonradiative recombination; photovoltaics; surface defects