The photophysical properties and structural features of distortion-stabilized K2AuIAuIIIX6 (X = Br, I) double perovskites

Mixed-valence (Cs2AuAuX6)-Au-I-X-III double perovskites (DPs) have aroused great interest because of their high stability and tunable band gap. In this research, the fundamental physical properties and photovoltaic performance of novel (K2AuAuX6)-Au-I-X-III (X = Br, I) DPs are thoroughly examined via first-principles calculations. According to our simulations, two highly distorted monoclinic structures are stabilized since their crystal stability is validated. The material ductility is disclosed for both compounds, which makes them suitable for thin-film solar cells. The predicted fundamental band gaps are within 1.0-1.1 eV, implying their potential suitability for efficient solar energy conversion. The optical features such as the optical absorption and photovoltaic performance are comprehensively evaluated. Their optical characteristics are similar to each other, and low reflectivity and energy loss are revealed. Meanwhile, their high solar absorption is undoubtedly observed. Consequently, the simulated conversion efficiencies of 26.1 % and 29.3 % are uncovered for (K2AuAuBr6)-Au-I-Br-III and (K2AuAuI6)-Au-I-I-III, respectively. The discovery of distortion-stabilized (K2AuAuX6)-Au-I-X-III DPs can provide an attractive perspective for discovering high-performance optoelectronic materials.