Lead acetate precursors for preparing CsPbI3 light harvester layers of inorganic perovskite solar cells

•a-CsPbI3 light harvester layers are prepared at low temperature without hydrogen iodide additive.•Lead acetate is used as the lead source of precursor solutions.•Ethylenediaminium iodide can cooperates with the lead acetate precursor.•The grain size of CsPbI3 layers is increased and their trap density is reduced.•The power conversion efficiency and photo-stability of devices are improved. CsPbI3 triggers strong interest in the photovoltaic community for their promising photoelectric property and nonvolatility. However, CsPbI3 layers with a-phase crystal structure are difficult for preparation, and these layers easily degrade to non-photoactive δ-phase at room temperature. Tuning the composition of precursor solutions is an important method for improving the properties of CsPbI3 layers. Herein, we prepare inorganic a-CsPbI3 perovskite solar cells using lead acetate as the lead source, which is different from conventional precursors with lead iodide as the lead source. The lead acetate precursor needs neither incorporating hydrogen iodide nor preparing PbI2 complex, and it is shown to enlarge the grain size, improve the crystallinity and reduce the trap density of CsPbI3 layers. By cooperating the lead acetate precursor with EDAI2 additive, the power conversion efficiency (PCE) of devices increases from 9.2% to 12.9% and the photo-stability of these devices is improved simultaneously.