Design, synthesis, optical studies, and application of all-inorganic layered double perovskites as stabilizers in ambient air processed perovskite solar cells

Five all-inorganic layered double perovskites including Cs4CuCr2Cl12, Cs4CuCo2Cl12, Cs4CuSb2Cl12, Cs4CuLa2Cl12, and Cs4CuCe2Cl12 were synthesized and their properties were investigated. Cs4CuSb2Cl12 with a suitable band gap near 1 eV, a truncated hexagonal trapezohedron morphology and large grains (5 µm) was added as the most favorable additive into CH3NH3PbI3 perovskite of ambient air processed perovskite solar cells (PSCs). The CH3NH3PbI3 films containing 1, 3, and 5% w/w of Cs4CuSb2Cl12 were studied. The PSC fabricated using the perovskite film containing 1% Cs4CuSb2Cl12 exhibited an increase of 20.32% in power conversion efficiency (PCE) compared with the device without the additive (from 5.66 to 6.81%). The Cs4CuSb2Cl12 additive significantly ameliorated the PSCs stability. These improvements were attributed to the large grain size, high electron-hole recombination resistance, low direct and indirect bandgaps (1.16 and 1.10 eV), strong light absorption, defects passivation, and structural stability of Cs4CuSb2Cl12 confirming this material is an effective candidate for PSCs fabrication.