Dynamic Insights into Charge Transport and Interface Recombination from Frequency Modulated Photocurrent Mapping
Felix Deschler a
a Technische Universität München, Karlstraße 45, München, 80333, Germany
Proceedings of International Conference on Impedance Spectroscopy and Related Techniques in Metal Halide Perovskites (PERIMPED)
Online, Spain, 2020 October 6th - 7th
Organizers: Juan Bisquert, Bruno Ehrler and Eline Hutter
Invited Speaker, Felix Deschler, presentation 018
Publication date: 25th September 2020

We report a novel photocurrent frequency modulation mapping technique, which enables us to achieve micrometer spatial and sub-microsecond temporal resolution of photocurrent transients. We employ our technique to report charge carrier recombination dynamics in hybrid perovskite bulk and selectively at interfaces with electrodes. We isolate and identify material-specific loss channels for device operation by characterizing the charge dynamics at interfaces with individual electrodes and charge selective layers. We further find a bulk charge trapping length for bulk hole traps of 21 μm with an associated trapping timescale of 2 μs, demonstrating that bulk trapping is not a major limiting factor for long-distance charge transport in perovskite-based devices. We determine the length and timescales of carrier transport via diffusion and photon recycling. We find significant photocurrent losses on and near gold electrodes due to the formation of a reduced charge carrier mobility region near the perovskite-gold interface with an associated trapping timescale of 0.7 μs. Our ability to expand the steady-state mechanisms of interface processes in space and time has potential to characterize a wide range of processes, which provides novel insights into device operation for high throughput optimization of optoelectronic and related energy applications.

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