Huge potentiality of lead halide perovskite nanocrystals (NCs) can be found in optoelectronic and photocatalytic fields. However, the main bottlenecks in photocatalysis are their toxicity and instability. To shake off these issues, lead-free Cs2AgBiX6 (X = Cl, Cl0.5Br0.5, Br, Br0.5I0.5, I) double perovskite NCs were synthesized by a simple antisolvent recrystallization approach. Moreover, the as-prepared Cs2AgBiX6 materials were systematically studied for photocatalytic CO2 reduction, which costed a total electron consumption of 37.8 μmol g–1 under visible light irradiation (λ ≥ 420 nm, 300 W Xe lamp) within 3 h for Cs2AgBiI6. Our study here provides novel ideas of lead-free perovskites for photocatalytic reduction of CO2.

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The photoreduction of CO 2 into renewable fuels is a promising approach to solve the global energy and environmental crisis. All-inorganic bismuth (Bi) halide perovskite nanocrystals (NCs) have emerged as an appealing photocatalyst for visible-light-driven CO 2 reduction, but they still have low photocatalytic activity. Herein, a set of lead-free and stable Cs 3 Bi 2 X 9 (X = Cl, Cl 0.5 Br 0.5 , Br, Br 0.5 I 0.5 , I) perovskite NCs were explored for the photocatalytic reduction of CO 2 to CO at the gas− solid interface. In all of the recorded perovskite NCs, the as-synthesized Cs 3 Bi 2 (Br 0.5 I 0.5 ) 9 showed the highest efficiency of CO 2 -to-CO conversion producing 54 μmol g −1 of CO yield under visible-light irradiation for 3 h. The strategy we proposed may bring up new opportunities for an efficient photocatalytic CO 2 reduction of lead-free perovskite NCs.

Nowadays, there is much attention focusing on lead halide perovskite because of its admirable performances in optoelectronic applications. However, the notorious toxicity and long-term instability are two main factors limiting its widespread applications. The findings of this work demonstrate a facile synthesis process for novel lead-free CsAgCl 2 perovskite microcrystals with no organic ligand involved. The fundamental properties of the CsAgCl 2 microcrystals are revealed by applying temperature-dependent X-ray diffraction and photoluminescence measurements from 77 to 300 K. Furthermore, the CsAgCl 2 microcrystals exhibit excellent air (60 days), thermal (100 °C), and light stability. Meanwhile, the CsAgCl 2 microcrystals have shown exciting potential applications in the fields of photocatalysis and photoelectrochemistry.

In recent years, it has been reported that using ligands modification to passivate the surface is one reasonable approach to improve the optical properties and stability of perovskite quantum dots (QDs). However, a simple and effective way to diminish the aggregation phenomenon of perovskite QDs is still challenging. Herein, a ligand‐engineering strategy is adopted to fabricate CsPbBr3 QDs by applying a shorter capping ligand octylamine (OLA) to replace the commonly used long ligand oleylamine (OAm). After the ligand modification, the photoluminescence quantum yield of CsPbBr3 QDs is enhanced from 62.4% to 91.3%. No aggregation or degradation phenomenon can be observed in solution even after being exposed to the air for 100 days. Moreover, the OLA‐CsPbBr3 QDs film can keep 96.8% of initial photoluminescence intensity even when stored under ambient condition for 5 weeks. Furthermore, the stimulated emission performance is investigated in terms of amplified spontaneous emission (ASE), and the ASE threshold of OLA‐CsPbBr3 QDs is only 24% of the OAm‐CsPbBr3 QDs threshold, and the ASE photostability is also enhanced. All the results suggest that the OLA ligand modification is an available strategy to improve the properties of CsPbBr3 QDs and to shed light on the potential practical applications for photoelectric devices.

Halide perovskites are potential humidity-detection materials due to their sensitivity to water, but the instability of traditional lead-based halide perovskites and the toxicity of Pb hinder further application in humidity sensing. Here, lead-free Cs 3 Cu 2 Br 5 perovskite microcrystals passivated by surface ligands (OLA and OAm) are used to prepare an environmentally friendly humidity sensor. The humidity sensing performance of the prepared sensors was tested, and the effect of surface ligands of perovskites on the performance of humidity sensors was analyzed. The results show that the impedance variations of the manufactured humidity sensors at 12 to 95% relative humidity are 10 6 Ω (OLA) and 10 5 Ω (OAm), respectively. Besides, the sensors demonstrated excellent repeatability, low hysteresis, and considerable stability at different RH values. Furthermore, the analysis of the different ligands attests that short-chain OLA is more conducive to the formation of porous films with stronger water absorption capacity, further improving the responsiveness of the sensor. By contrast, and long-chain OAm is more conducive to the formation of dense films, improving the response ability at low humidity. Additionally, the more hydrophilic OLA contributes to greater responsiveness, while the more hydrophobic OAm helps to shorten the response and recovery time.

A huge prospect of lead halide perovskites can be found in the fields of optoelectronics and photocatalysis. However, the main obstacle to their photocatalytic application is their toxicity. To shake off these issues, lead-free Cs 3 Sb 2 I 9 perovskite microcrystals with different morphologies were synthesized via a simple hot-injection approach. Furthermore, the as-prepared Cs 3 Sb 2 I 9 microcrystals were utilized for photocatalytic CO 2 reduction, achieving a total electron yield of 14.2 μmol g −1 under visible-light irradiation (λ ≥ 420 nm, 300 W Xe lamp) within 3 h. Our work here provides an idea for the application of lead-free perovskites for photocatalytic CO 2 reduction.

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