KBaTeBiO₆: A Lead-Free, Inorganic Double-Perovskite Semiconductor for Photovoltaic Applications

Solar cells made up of lead-halide perovskites have shown a remarkable increase in power conversion efficiency; however, they are plagued with instability issues that, combined with the toxicity of lead, have led to a search for new semiconductors made up of heavy and nontoxic metals such as bismuth. Here, we report on a new, inorganic, double perovskite oxide semiconductor: KBaTeBiO₆, which has an experimental indirect band gap of 1.88 eV and shows excellent stability. We combined data analytics and high throughput density functional theory calculations to search through thousands of hypothetical inorganic double perovskite oxides containing bismuth and predict KBaTeBiO₆ as a potential photovoltaic material, which was subsequently synthesized using a wet-chemistry route. The calculated effective mass of the charge carriers for KBaTeBiO₆ is comparable to the best performing Bi-halide double perovskites. Our work demonstrates the untapped potential of inorganic Bi-based double perovskite oxides - that offer the ability to change both the cation combination and their stoichiometry to achieve desired electronic properties - as exciting, benign, and stable alternatives to lead-halide perovskites for various semiconducting applications.