Halide perovskites have experienced a huge development in the past years, but they still have two major challenges for their massive implantation: the long-term stability and the use of lead. One of the most obvious lead-free candidates to replace these perovskites is CsSnI 3 but, due to its poor environmental stability, it has been discarded for the fabrication of stable devices. Nevertheless, ambient degradation of CsSnI 3 and ulterior reconstruction produces relatively stable lead-free Cs 2

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... nI 6 double perovskite with interesting optical properties that have not been deeply characterized previously. In this work, the potentiality of the optical properties of Cs 2 SnI 6 is studied and compared with the most common halide perovskite, CH 3 NH 3 PbI 3 (MAPbI 3 ). The Cs 2 SnI 6 films stayed in standard atmosphere during a week without showing any signs of degradation. They also demonstrated better reflective behavior than MAPbI 3 and higher absorption in the 650 nm and 730 nm spectral range, making this material interesting for the development of photodetectors in this region. This study demonstrates that Cs 2 SnI 6 is a promising material for photo-devices, as it highlights its main characteristics and optical parameters, giving an original view on the use of the double perovskite, but at the same time emphasizing the need to improve the electrical properties for the development of efficient optoelectronic devices.