MIXED TIN AND GERMANIUM PEROVSKITES
Perovskite materials useful in the manufacture of photovoltaic cells are provided. The perovskite materials have the formula AB′ 0.5 B″ 0.5 X 3 or A′ 0.5 A″ 0.5 B′ 0.5 B″ 0.5 X 3 , wherein A, A′, and A″ are organic or inorganic cations, X is a halogen ion, B′ is tin, and B″ is germanium. Embodiments of the mixed tin and germanium halide perovskite materials possess a direct bandgap within the optimal range of 0.9-1.6 eV and have an optical absorption spectrum that is comparable to the state-of-the-art methylammonium lead iodide perovskites. The perovskite materials provided herein have been formulated to be lead-free.
1 . A perovskite material having the formula AB′ 0.5 B″ 0.5 X 3 , wherein A is an organic or inorganic cation, X is a halogen ion, B′ is tin, and B″ is germanium.
2 . The perovskite material of claim 1 , wherein A is cesium.
3 . The perovskite material of claim 2 , wherein X is iodide or bromide.
4 . The perovskite material of claim 1 , wherein A is rubidium.
5 . The perovskite material of claim 4 , wherein X is iodide or bromide.
6 . The perovskite material of claim 1 , wherein A is methylammonium.
7 . The perovskite material of claim 1 , wherein A is formamidinium.
8 . The perovskite material of claim 1 , wherein X is iodide.
9 . The perovskite material of claim 1 , wherein X is bromide.
10 . A photovoltaic cell comprising a substrate, a blocking layer, an optical absorption material comprising the perovskite material of claim 1 , a hole-transporting material, and an electrode.
11 . A perovskite material having the formula A′ 0.5 A″ 0.5 B′ 0.5 B″ 0.5 X 3 , wherein A′ is an inorganic cation and A″ is an organic cation, X is a halogen ion, B′ is tin, and B″ is germanium.
12 . The perovskite material of claim 11 , wherein A′ is cesium and A″ is methylammonium.
13 . The perovskite material of claim 12 , wherein X is iodide.
14 . The perovskite material of claim 11 , wherein A′ is rubidium, and A″ is methylammonium.
15 . The perovskite material of claim 14 , wherein X is iodide.
16 . The perovskite material of claim 11 , wherein A′ is cesium and A″ is formamidinium.
17 . The perovskite material of claim 16 , wherein X is iodide.
18 . The perovskite material of claim 11 , wherein A′ is rubidium and A″ is formamidinium.
19 . The perovskite material of claim 18 , wherein X is iodide.
20 . The perovskite material of claim 11 , wherein X is iodide.
21 . A photovoltaic cell comprising a substrate, an electron-transporting layer, an optical absorption material comprising the perovskite material of claim 11 , a hole-transporting material, and an electrode.