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Enhanced Visible Light Absorption for Lead-free Double Perovskite Cs2AgSbBr6

last modified Mar 12, 2019 08:17 PM

Enhanced visible light absorption for lead-free double perovskite Cs2AgSbBr6

Fengxia Wei, Zeyu Deng, Shijing Sun, Noor Titan Putri Hartono, Hwee Leng Seng, Tonio Buonassisi, Paul D Bristowe and Anthony K Cheetham

12th March 2019

Abstract

In a search for Pb-free photovoltaic materials, a double perovskite Cs2AgSbBr6with an indirect optical bandgap of 1.64 eV has been synthesized. Single crystal X-ray diffraction determined the space group as Fm-3m with a = 11.1583(7) Å. The black, as-synthesised compound turned brown after heat treatment at 480 K while the symmetry and crystallinity were preserved. X-ray photoelectron spectroscopy indicated the existence of Sb5+in the black crystals, suggesting that the dark colour arises from the Sb3+-Sb5+charge transfer. Furthermore, UV visible spectroscopy and density functional theory calculations have been applied to probe the optical properties and electronic structure.