Titanium-Based Vacancy-Ordered Double Halide Family in Perovskite Solar Cells

The toxicity and stability risk of perovskite structured materials have raised concerns in respective to utilization as a solar energy conversion material. The most common perovskite structured material is lead (Pb)-based, which is an element that is knowingly toxic to humans and the environment. Although the stability issue has been well allayed with several optimizations, the ruinous Pb remains a future challenge for perovskite solar cells. Compositional and structural derivatives of the perovskite family, specifically vacancy-ordered double halide perovskites (DHPs), have attracted the attention of researchers in terms of efficiency and toxicity issues subjugation. Although tin (Sn)-based vacancy-ordered DHPs have been widely explored, the intrinsic property conduces low performance output. Titanium (Ti) is a potential substituting candidate of Sn in a vacancy-ordered DHPs structure. It is an environment-friendly element ideal for sustainable perovskite structured compositions. Rudimentary studies of Ti-based vacancy-ordered DHPs emphasized its potential development as an eco-friendly and stable solar cell. In promoting the development of Ti-based vacancy-ordered DHPs as potential absorbers, we summarized herein the recent progress of experimental and theoretical studies of this perovskite material.