Mapping Bulk and Interfacial Charge Carrier Recombination Dynamics in Perovskite Optoelectronic Devices
Haralds Abolins a, Arjun Ashoka a, Yu-Hsien Chiang a, Gregory Tainter a b, Bart Roose a, Hannah Joyce b, Stephan Hofmann b, Jack Alexander-Webber b, Richard Friend a, Felix Deschler c
a Cavendish Laboratory, University of Cambridge - UK, JJ Thomson Avenue, 9, Cambridge, United Kingdom
b University of Cambridge, Department of Engineering, UK, JJ Thomson Avenue, 9, Cambridge, United Kingdom
c Technical University Munich, Walter-Schottky-Institute, Physics Department, Am Coulombwall, 4, Garching bei München, 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
Oral, Haralds Abolins, presentation 016
Publication date: 25th September 2020

We report the in-operando charge carrier recombination dynamics in perovskite bulk and at interfaces with electrodes by employing a novel photocurrent modulation technique, which enables us to achieve micrometre spatial and sub-microsecond temporal resolution of photocurrent transients. Our capacity to identify and isolate significant loss channels for device operation, by characterizing the performance of individual electrodes and charge selective layers, has previously only been achieved via indirect techniques. We find a 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 observe 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. We further determine the length and timescales of carrier transport via diffusion and photon recycling. Our novel ability to expand the steady-state operation of the device in space and time allows us to characterise a broad range of processes in-operando with crucial insights into device operation, and paves the way for high throughput optimisation of interfaces for high-efficiency optoelectronics.

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