Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
DOI: https://doi.org/10.29363/nanoge.matsus.2023.165
Publication date: 22nd December 2022
Metal-Halide perovskite materials are known to be of high potential for solar and LED applications thanks to their very high absorption coefficients, remarkably long carrier-lifetime and high photoluminescence quantum yield in comparison to traditional semiconductor absorbers [1], [2]. This is particularly remarkable given that high materials quality can be obtained even when samples are grown from solutions. It seems that not only their defect tolerance but, even more so, the self-healing ability of halide perovskites are a fundamental reason for their excellent opto-electronic properties. Nevertheless, dynamic effects also give rise to a number of meta-stabilities. Materials can be degraded and temporarily perturbed under external stressors, such as light and bias [3],[4],[5]. In this work, we focus on methyl-ammonium lead tri-bromide microplatelets, prepared following the work from Mao et. al. [6]. We use these microplatelets to study fundamental dynamics of charge carriers interacting with physical or light-induced defects generated in these crystals by external perturbation. The samples can be considered an idealized model-system that exclude typical intra-grain boundaries of polycrystalline thin film samples, thus removing the different phenomena that could occur at these local sites.
Within these model systems, we show a correlation between time-resolved photoluminescence decay dynamics and sample properties, perturbed by the history of the micro-sized sample to illumination, generating light-induced defects; or mechanical stress, generating structural defects. We utilized excitation-intensity and repetition rate-dependent photoluminescence measurements [7] to provide a "finger print" of samples exposed to different degrading conditions to investigate the characteristic difference between light- and mechanically-induced defects affecting the charge carrier dynamics within the crystal.
Finally, we refined a numerical model to fit photoluminescence lifetime data based on population rate equations, including trapped populations [8],[9]. A fit of the presented data is used to see how material properties, such as trap densities, are affected by illumination intensity and/or repetition rate.
I thank Prof. Eva Unger, Dr. Rowan McQueen for their help and supervision. As well as the HI-SCORE program for funding.
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