Boosting structural stability of lead-free Tin-based layered double perovskite nanocrystals with enhanced photoelectrochemical activity

Recently, a new family of quasi-2D lead-free layered double perovskites in a formula Cs 4 M(II)M(III) 2 Cl 12 has attracted increasing attention, particularly in the form of colloidal nanocrystals (NCs). Herein, we successfully coordinate Sn(II) at M(II) site in this layered structure while tailoring M(III) site with two types of trivalent cations, eventually forming Cs 4 SnIn 2 Cl 12 (CTIC) and Cs 4 SnSb 2 Cl 12 (CTAC) NCs. We observe the formation of a self-trapped excited state in both cases. CTIC exhibits bright transition with a relatively high photoluminescence quantum yield of 12%. Both NCs are employed as photoanodes to construct a photoelectrochemical (PEC) cell for realizing a redox reaction with benzoquinone as the intermediate reactant. CTAC achieves the highest photocurrent density (60 µA cm -2 ) under 1 Sun condition, which is amongst the highest for lead-free perovskite PEC reactions. More importantly, the Sn(II) cation state of CTIC NCs can be maintained even after 300 days of air storage, highlighting the effectiveness of this new quasi-2D layered structure on stabilizing Sn(II) perovskites.