Lead-Free Halide Double Perovskites via Heterovalent Substitution of Noble Metals

TL;DR

This study introduces a new class of lead-free halide double perovskites based on noble metals, demonstrating promising optoelectronic properties and stability, with successful synthesis and detailed characterization of Cs2BiAgCl6.

Contribution

The paper reports the computational design and experimental synthesis of novel Pb-free double perovskites using noble metals, expanding the materials options for stable optoelectronic applications.

Findings

Promising tunable band gaps in the visible range.

Successful synthesis and structural characterization of Cs2BiAgCl6.

Demonstrated ambient stability of the new perovskite.

Abstract

Lead-based halide perovskites are emerging as the most promising class of materials for next generation optoelectronics. However, despite the enormous success of lead-halide perovskite solar cells, the issues of stability and toxicity are yet to be resolved. Here we report on the computational design and the experimental synthesis of a new family of Pb-free inorganic halide double-perovskites based on bismuth or antimony and noble metals. Using first-principles calculations we show that this hitherto unknown family of perovskites exhibits very promising optoelectronic properties, such as tunable band gaps in the visible range and low carrier effective masses. Furthermore, we successfully synthesize the double perovskite Cs2BiAgCl6, we perform structural refinement using single-crystal X-ray diffraction, and we characterize its optical properties via optical absorption and photoluminescence measurements. This new perovskite belongs to the Fm-3m space group, and consists of BiCl6 and AgCl6 octahedra alternating in a rock-salt face-centered cubic structure. From UV-Vis and PL measurements we obtain an indirect gap of 2.2 eV. The new compound is very stable under ambient conditions.