Summary Lead halide perovskites are prospective candidates for CO 2 photoconversion. Herein, we report copper-doped lead-free Cs 2 AgSbCl 6 double perovskite microcrystals (MCs) for gas-solid phase photocatalytic CO 2 reduction. The 0.2Cu@Cs 2 AgSbCl 6 double perovskite MCs display unprecedented CO 2 photoreduction capability with CO and CH 4 yields of 412 and 128 μmol g −1 , respectively. The ultrafast transient absorption spectroscopy reveals the enhanced separation of photoexcited carriers in copper-doped Cs 2 AgSbCl 6 MCs. The active sites and reaction intermediates on the surface of the doped Cs 2 AgSbCl 6 are dynamically monitored and precisely unraveled based on the in-situ Fourier transform infrared spectroscopy investigation. In combination with density functional theory calculations, it is revealed that the copper-doped Cs 2 AgSbCl 6 MCs facilitate sturdy CO 2 adsorption and activation and strikingly enhance the photocatalytic performance. This work offers an in-depth interpretation of the photocatalytic mechanism of Cs 2 AgSbCl 6 doped with copper, which may provide guidance for future design of high-performance photocatalysts for solar fuel production.
Jun Zhou,Ximing Rong,Maxim S. Molokeev,Xiuwen Zhang,Zhiguo Xia
The electronic and optical properties of perovskites are related to the local structures of the compounds and define their functional applications. Herein we have prepared a double perovskite Cs2AgSbCl6, which crystallized in the cubic structure with the space group Fm-3m and the material is found to have a varied band gap associated with different body colors. The anti-site defect model was established to investigate transposition influence on the optical and electronic properties of the double-perovskite Cs2AgSbCl6, and the proposed model clearly explained the as-observed variable body color. Cs2AgSbCl6 perovskite has a high decomposition temperature and is stable upon prolonged exposure to air and moisture, which emphasize its potential in the field of photovoltaic absorbers and optoelectronic applications.
Sb-based metal halide double perovskites (MHDPs) are promising lead-free luminescent materials owing to their potential to exhibit a unique broadband self-trapped exciton emission. However, pristine Sb-based MHDPs are generally non-luminescent, limited by the severe lattice distortion from stereochemically active 5 s 2 lone pairs of Sb 3+ and concentration quenching from dense [SbCl 6 ] 3- center packing. Alloying is a powerful strategy to modulate the optical properties of MHDPs. Herein, a series of Cs 2 AgSb 1-x In x Cl 6 (x = 0–0.4) samples were synthesized via a vacuum solid-state reaction. Combined with first-principles calculations, we elucidated the effects of In 3+ incorporation on their structural, electronic, and optical properties. The results reveal that In 3+ alloying not only spatially separates [SbCl 6 ] 3- luminescent centers to suppress concentration quenching, but also drives electron density redistribution, forming bond differentiation between ionic In-Cl bonds and reinforced covalent Sb-Cl bonds. Thus, lattice rigidity increases, which alleviates excessive distortion of [SbCl 6 ] 3- octahedra, so as to reduce electron-phonon coupling strength. Consequently, non-radiative recombination caused by concentration quenching and excessive [SbCl 6 ] 3- octahedral distortion in Cs 2 AgSbCl 6 is largely suppressed with In 3+ alloying, which prolongs the photoluminescence lifetime from 0.37 μs (x = 0.05) to 1.23 μs (x = 0.3) and enables a transformation from non-luminescence to bright yellow-green emission across the Cs 2 AgSb 1-x In x Cl 6 (x = 0–0.4) system. The Cs 2 AgSb 0.7 In 0.3 Cl 6 sample exhibits the highest PL intensity with a PLQY of 11.88%. This study demonstrates that In 3+ alloying can simultaneously mitigate concentration quenching and lattice distortion in Sb-based MHDPs, providing a facile and effective strategy for developing high-performance lead-free luminescent materials.
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