Double perovskites have emerged as promising alternatives to lead halide perovskites, aiming to mitigate challenges related to toxicity and chemical instability. Among them, mixed-valence gold halides such as Cs2Au+Au3+Cl6, which contain only a single type of metal cation in two oxidation states, stand out due to their unique structural and electronic properties. These materials exhibit strong absorption in the near-infrared range, making them attractive candidates for optoelectronic applications such as photovoltaics. In this work, we employ temperature-dependent optical spectroscopy techniques to demonstrate that these compounds exhibit particularly strong polar electron-phonon coupling, which has a profound impact on their optoelectronic properties. In particular, this coupling gives rise to a temperature-dependent absorption tail that reshapes the global spectral spectrum. We show that this tail leads to a forbidden band-egde recombination, which explains the reported difficulties in detecting a photoluminescence signal from this class of double perovskites.
@article{arxiv.2505.01904,
title = {Polar Indirect Valley as a Limiting Factor for Radiative Efficiency in Gold-Based Mixed-Valence Double Perovskites},
author = {Ange B. Chambissie Kameni and Alexandre Py-Renaudie and Damien Garrot and Baptiste Berenguier and Guillaume Bouchez and Davide Raffaele Ceratti and Philip Schulz and Jean-François Guillemoles and Géraud Delport},
journal= {arXiv preprint arXiv:2505.01904},
year = {2025}
}