For the first time, a new lead-free double perovskite Cs2NaBiI6 material was synthesized and applied to the perovskite solar cells.

All-inorganic perovskites are attracting increasing attention due to their superior thermal stability than that of the traditional CH 3 NH 3 PbI 3 , while their inferior phase stability in ambient conditions is still an unsolved issue. Here, for the first time, we report the incorporation of niobium (Nb 5+ ) ions into the CsPbI 2 Br perovskite. Results indicate that Nb 5+ can effectively stabilize the photoactive α-CsPbI 2 Br phase by the possible substitution of Pb 2+ . With 0.5% Nb doping, the carbon electrode-based all-inorganic perovskite solar cells achieved a high photoconversion efficiency value of 10.42%, 15% higher than that of the control device. The Nb 5+ incorporation reduces the charge recombination in the perovskite, leading to a champion V oc value of 1.27 V and a negligible hysteresis effect. This work explicates the high compatibility of all-inorganic perovskite materials and unlocks the opportunities for the use of high-valence ions for perovskite property modification.

Low-dimensional all-inorganic metal halide perovskites have been demonstrated as excellent building blocks for high-performance optoelectronic devices. Although many progresses have been achieved in low-dimensional all-inorganic perovskites, the substitution of toxic Pb is urgent for further optoelectronic applications. Here, we present the growth of lead-free all-inorganic CsSnX 3 (X = Cl, Br, and I) perovskite nanowire (NW) arrays on a mica substrate by a solid-source chemical vapor deposition method. All of the lead-free all-inorganic CsSnX 3 perovskite NW arrays epitaxially grow on the mica substrate to form equilateral triangles. The band gaps of the as-prepared CsSnX 3 perovskite NW arrays decrease from 1.84 to 1.34 eV with X changes from Br to I. The high crystallinity is confirmed by the strong photoluminescence (PL) emission peaks and uniform twodimensional PL mapping images. In the end, the as-prepared high-quality CsSnI 3 perovskite NW array is then configured into a near-infrared photodetector for the first time, exhibiting fast rise and decay time constants of 83.8 and 243.4 ms, respectively. All of the results present an important advance in the field of low-dimensional all-inorganic perovskites.

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