A Bismuth-Halide Double Perovskite with Long Carrier Recombination Lifetime for Photovoltaic Applications

Despite the remarkable rise in efficiencies
of solar cells containing
the lead-halide perovskite absorbers RPbX3 (R = organic
cation; X = Br– or I–), the toxicity
of lead remains a concern for the large-scale implementation of this
technology. This has spurred the search for lead-free materials with
similar optoelectronic properties. Here, we use the double-perovskite
structure to incorporate nontoxic Bi3+ into the perovskite
lattice in Cs2AgBiBr6 (1). The
solid shows a long room-temperature fundamental photoluminescence
(PL) lifetime of ca. 660 ns, which is very encouraging for photovoltaic
applications. Comparison between single-crystal and powder PL decay
curves of 1 suggests inherently high defect tolerance.
The material has an indirect bandgap of 1.95 eV, suited for a tandem
solar cell. Furthermore, 1 is significantly more heat
and moisture stable compared to (MA)­PbI3. The extremely
promising optical and physical properties of 1 shown
here motivate further exploration of both inorganic and hybrid halide
double perovskites for photovoltaics and other optoelectronics.