Degradation mechanism of hybrid tin-based perovskite solar cells and the critical role of tin (IV) iodide

Tin perovskites have emerged as promising alternatives to toxic lead perovskites in next-generation photovoltaics, but their poor environmental stability remains an obstacle towards more competitive performances. Therefore, a full understanding of their decomposition processes is needed to address these stability issues. Herein, we elucidate the degradation mechanism of 2D/3D tin perovskite films based on (PEA)0.2(FA)0.8SnI3 (where PEA is phenylethylammonium and FA is formamidinium). We show that SnI4, a product of the oxygen-induced degradation of tin perovskite, quickly evolves into iodine via the combined action of moisture and oxygen. We identify iodine as a highly aggressive species that can further oxidise the perovskite to more SnI4, establishing a cyclic degradation mechanism. Perovskite stability is then observed to strongly depend on the hole transport layer chosen as the substrate, which is exploited to tackle film degradation. These key insights will enable the future design and optimisation of stable tin-based perovskite optoelectronics

P2P Scalable Video Streaming Using Data Priority and FEC-based Noncooperative Multiple Description

Recent years have assisted the proliferation of peer-to-peer (P2P) communications in streaming audio/visual contents over widely-distributed networks. This widespreading has also fostered the need for efficient video coding and trans- mission strategies. The paper present an MD coding and packet classification strategy that improves a traditional Mul- tiple Description scheme basde on a scalable video coder and FEC codes via effective Unequal Error Protection and QoS classification. The proposed strategy uses a low-complexity packet prioritization strategy based on dependencies between video coding units to estimate the distortion associated to their loss. These data will be then used to tune the protec- tion level of video packets and optimize the classification via Game Theory based approach. The paper compares the performance of the different configurations of the proposed approach with some state-of-the-art solutions (like srTCM) showing a quality improvement up to 6 dB