Air Stable, High‐Efficiency, Pt‐Based Halide Perovskite Solar Cells with Long Carrier Lifetimes

The search for Pb‐free perovskite materials continues with limited success to find a suitable replacement for Pb with outstanding optoelectronic properties. Herein, Pb‐free inorganic halide perovskite Cs 2 PtI 6 with excellent absorption coefficient, long minority carrier lifetime, and optical bandgap of 1.4 eV is reported. Atmospheric precursor‐based solution processing results in high‐quality Cs 2 PtI 6 with absorption coefficient of for photon energies of >1.5 eV and high minority carrier lifetimes of >2 μs indicating low defect density in the material. Superstrate n–i–p solar cells processed with the structure F:SnO 2 /CdS/Cs 2 PtI 6 /carbon/Cu show promising device efficiency of 13.88%. These planar devices processed under atmospheric conditions show low V oc deficit (<0.3 V) without any hysteresis in forward and reverse scans indicating low trap densities. Pt offers an excellent model system for the replacement of Pb due to high atomic number, oxidation resistance, and stability. Cs 2 PtI 6 is an atmospherically stable phase under AM1.5G at 65 °C for 1000 h.