Promising Lead-Free Double-Perovskite Photovoltaic Materials Cs2MM′Br6 (M = Cu, Ag, and Au; M′ = Ga, In, Sb, and Bi) with an Ideal Band Gap and High Power Conversion Efficiency

Inorganic-organic hybrid halide perovskite MAPbI(3) (MA = CH3NH3) has attracted much attention because of its suitable band gap and strong visible-light absorption ability. However, intrinsic Pb toxicity and poor stability have hindered its further application in photovoltaic devices. Recently, Cs-based inorganic double perovskites with good stability and prominent light absorption have drawn substantial interest. Here, we have systematically investigated the electronic and optical properties of lead-free double perovskite Cs2MM'Br-6 (M = Cu, Ag, and Au; M' = Ga, In, Sb, and Bi) from first-principles calculations. Our results indicate that candidates have high stability against decomposition. The absorption coefficient of all double perovskites in the visible-light region can reach similar to 10(5) cm(-1). Direct band gaps (similar to 1.47 eV of Cs2AgInBr6 and similar to 1.37 eV of Cs2AgGaBr6) are close to the optimal value (1.34 eV) requested by the Shockley-Queisser limit. The spectroscopic limited maximum efficiency (similar to 31.9% of Cs2AgInBr6 and similar to 32.45% of Cs2AgGaBr6) can be obtained at the thickness of 1.5 mu m. The electron mobility in Cs2AgGaBr6 is up to 160.8 cm(2) V-1 s(-1), similar to that of MAPbI(3) (165 cm(2) V-1 s(-1)). Our studies provide a helpful guide to designing excellent lead-free absorber layers and give a new insight into the nature of double perovskites for developing novel optoelectronic devices for renewable solar energy utilization.

Automated summary

The study systematically investigates the electronic and optical properties of lead-free double perovskite Cs2MM'Br-6 using first-principles calculations, revealing high stability and strong light absorption capabilities. The absorption coefficient in the visible-light region is found to be significant, with potential for practical applications. The results indicate promising potential for developing novel optoelectronic devices for renewable solar energy utilization.