Planar FAPbBr₃ Solar Cells with Power Conversion Efficiency above 10%

Bromide-based hybrid perovskites are of particular interest not only due to the fact that they offer a way to go beyond the Shockley–Queisser limit via the tandem cell scheme but single-junction devices of them can also achieve reasonably high efficiency with high stability for solar energy conversion. However, the highest power conversion efficiency achieved up to now for FAPbBr3 single-junction solar cells is only 8.2%, which is far below the efficiency of ∼17% predicted from detailed balance analysis. Here, a two-step method (the intermolecule exchange pathway) was systematically optimized for the fabrication of high-quality FAPbBr3 films. A molecule of urea, structurally similar to formamidinium, is introduced as an additive to tune the intermolecular ion exchange procedure. SnO2 is introduced as an electron-selective contact to the planar structured FAPbBr3 solar cells. As a result, a power conversion efficiency of 10.61% and a Voc of 1.56 V are achieved with planar structured solar cells, both of which represent the highest value ever reported for FAPbBr3 solar cells.