Madeleine Breshears1,Rajiv Giridharagopal1,David Ginger1
University of Washington1
Madeleine Breshears1,Rajiv Giridharagopal1,David Ginger1
University of Washington1
Traditional optical methods of measuring the spatial heterogeneity of carrier lifetimes—such as fluorescence lifetime imaging (FLIM)—are diffraction-limited, whereas perovskite materials of interest exhibit grain structure at lengthscales far below the diffraction limit. Here, we use time-resolved electrostatic force microscopy (trEFM) to achieve nanoscale spatial resolution of carrier dynamics. trEFM captures the response of the scanning probe cantilever to a perturbation of the electrostatic force gradient between the tip and sample; by monitoring the cantilever oscillation during photoexcitation as a function of wavelength and intensity, we can measure carrier recombination with sub-microsecond temporal resolution. Using this method, we observe slower recombination dynamics in FA<sub>0.83</sub>Cs<sub>0.17</sub>Pb(Br<sub>0.15</sub>I<sub>0.85</sub>)<sub>3</sub> on a phosphonic acid-based hole transport layer (HTL) as compared to indium tin oxide substrates, which we correlate these findings with bulk lifetime measurements and FLIM. Finally, we apply trEFM to investigate the spatial heterogeneity in carrier dynamics of a FA<sub>0.83</sub>Cs<sub>0.17</sub>Pb(Br<sub>0.15</sub>I<sub>0.85</sub>)<sub>3</sub> when passivated with (3-aminopropyl)trimethoxysilane (APTMS), demonstrating that APTMS-passivation extends carrier recombination lifetimes in perovskite.