How Shallow Traps Lead to Long and Variable Charge Carrier Decay Times in Lead Halide Perovskites
Chris Dreessen a, Yuan Ye a, Genghua Yan a, Toby Rudolph a, Markus Hülsbeck a, Benjamin Klingebiel a, Jiajiu Ye a, Uwe Rau a, Thomas Kirchartz a
a IEK-5 Photovoltaik, Forschungszentrum Jülich GmbH, Germany, 52425 Jülich, Germany
b Faculty of Engineering and CENIDE, University of Duisburg-Essen, Carl-Benz-Straße, 199, Duisburg, Germany
Oral, Chris Dreessen, presentation 048
Publication date: 6th February 2024

Quantifying recombination in halide perovskites is essential for controlling and enhancing the performance of perovskite solar cells. Here, we present a comprehensive analysis of recombination dynamics in lead halide perovskites via transient and steady-state photoluminescence, focusing on the impact of the energetic position of electronic traps. We emphasize that the decay times extracted from transient photoluminescence measurements cannot generally be reduced to a single value but rather depend strongly on the charge carrier concentration. It follows that the magnitude of the decay time is reliant on the sensitivity of the measurement. We show photoluminescence decay curves with a large dynamic range of more than 10 orders of magnitude that demonstrate decay times from tens of nanoseconds up to hundreds of microseconds in perovskite films. Assuming, that these long decay times correspond to the lifetime of a deep trap in steady state, one would expect a material with perfect photoluminescence quantum yield, which does however not coincide with the experimental findings. Instead, the decay times in transient measurements are affected by charge trapping and detrapping. We quantitatively explain both the transient and steady-state photoluminescence with the presence of a high density of shallow traps without the influence of deep traps. In summary, this study offers a deeper understanding of recombination dynamics in halide perovskites through the analysis of transient and steady-state measurements. Our findings underscore the importance of considering the influence of shallow traps in interpreting decay times and optimizing device performance.

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