A low concentration of Te4+ doping is found to be capable of endowing the lead‐free Cs2SnCl6 perovskites with excellent photoluminescence quantum yield (PLQY), while further increasing Te4+ concentration leads to PLQY deterioration. The mechanism behind the improved PLQY is intensively studied and reported elsewhere. However, little work is conducted to understand the decreased PLQY at high doping levels and to explore its implications for non‐PL‐related applications. Here, it is demonstrated that the Te4+‐incorporated Cs2SnCl6 can be promising candidate for efficient CO2 photocatalysis. An optimum photocatalytic performance is achieved when Te4+ concentration reaches as high as 50%, at which point significant PL quenching has occurred. Through a detailed spectral characterization, such concentration‐dependent functionality is attributed to systematic changes in both electronic and local crystal structure, which allow a robust regulation of excitation energy relaxation channels. These findings expand the scope of available photocatalysts for CO2 reduction and also inform synthetic planning for the preparation of multifunctional Pb‐free metal halide perovskites.
Low dimensional lead‐free metal halides have become the spotlight of the research on developing multifunctional optoelectronic materials as their properties show a wide range of tunability. However, most reported low dimensional metal halides only function in the ultra‐violet to visible range due to their large bandgap. Moreover, the organic cation based low dimensional metal halides show limited thermal stability; on the other hand, their inorganic cation based counterparts suffer from limited solution processability. A hybrid cation approach is proposed, where a zero dimensional (0D) metal halide ((DFPD)2CsBiI6) is developed by using mixed organic–inorganic cations: 4, 4‐difluoropiperidine (DFPD) and cesium (Cs+). This ensures both thermal stability and solution processability. Furthermore, [BiI6]3− octahedra are serving as active light absorption units, which ensures the bandgap to be located at the visible region. Its photoluminescence (PL) is further shifted to the near infrared (NIR) region by doping (DFPD)2CsBiI6 with antimony (Sb3+). The developed materials show multifunctional properties: thermochromic behavior, light detection, and NIR light emitting. This study expands the scope of developing multifunctional 0D metal halides.
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