Lead-free Perovskite Materials (NH4 )3 Sb2 Ix Br9-x.

A family of perovskite light absorbers (NH4 )3 Sb2 Ix Br9-x (0≤x≤9) was prepared. These materials show good solubility in ethanol, a low-cost, hypotoxic, and environmentally friendly solvent. The light absorption of (NH4 )3 Sb2 Ix Br9-x films can be tuned by adjusting I and Br content. The absorption onset for (NH4 )3 Sb2 Ix Br9-x films changes from 558 nm to 453 nm as x changes from 9 to 0. (NH4 )3 Sb2 I9 single crystals were prepared, exhibiting a hole mobility of 4.8 cm2  V-1  s-1 and an electron mobility of 12.3 cm2  V-1  s-1 . (NH4 )3 Sb2 I9 solar cells gave an open-circuit voltage of 1.03 V and a power conversion efficiency of 0.51 %.