Sub-10 fs Time-Resolved Vibronic Optical Microscopy

Abstract

We introduce femtosecond wide-field transient absorption microscopy combining sub-10 fs pump and probe pulses covering the complete visible (500–650 nm) and near-infrared (650–950 nm) spectrum with diffraction-limited optical resolution. We demonstrate the capabilities of our system by reporting the spatially- and spectrally-resolved transient electronic response of MAPbI3–xClx perovskite films and reveal significant quenching of the transient bleach signal at grain boundaries. The unprecedented temporal resolution enables us to directly observe the formation of band-gap renormalization, completed in 25 fs after photoexcitation. In addition, we acquire hyperspectral Raman maps of TIPS pentacene films with sub-400 nm spatial and sub-15 cm–1 spectral resolution covering the 100–2000 cm–1 window. Our approach opens up the possibility of studying ultrafast dynamics on nanometer length and femtosecond time scales in a variety of two-dimensional and nanoscopic systems.

Grain Boundaries Act as Solid Walls for Charge Carrier Diffusion in Large Crystal MAPI Thin Films

“…We would like to emphasize here that this distinction is difficult to make with other methods, employing large area illumination. 41 The influence of restricted diffusion has been reported before for single crystalline MAPI particles by Jin et al 15,23 as well as for thin film microcrystals by Yang et al 29 by means of microscopy, which is in agreement with our results. Both groups found no evidence for enhanced quenching or nonradiative decay at the grain boundaries.…”

Understanding the visible-light photocatalytic activity of GaN:ZnO solid solution: the role of Rh2−yCryO3 cocatalyst and charge carrier lifetimes over tens of seconds

“…Spatially-resolved measurements relating the structure to the charge carrier dynamics would be particularly insightful. 91 , 92 Further investigations of the presence and role of heterojunctions on the nanoscale between GaN and ZnO phases could lead to a more complete understanding of GaN:ZnO and other particulate photocatalysts.…”

Spatially-resolved fluorescence-detected two-dimensional electronic spectroscopy probes varying excitonic structure in photosynthetic bacteria

“…Similarly, the effect of grain size 25 and chloride content 26 on charge transport in perovskites thin-films is well known, but the connections between layer heterogeneity and charge delocalization is poorly understood. Spatial-resolution provided by pump-probe microscopy has partly addressed these questions 11 , 27 – 29 . However, new spatially resolved tools that can go beyond pump-probe approaches to resolve inhomogeneity and the couplings between excited electronic states directly with high frequency and time-resolution could impact our understanding of a broad range of systems, including emerging 2D materials 30 .…”