Ethanol stabilized precursors for highly reproducible printable mesoscopic perovskite solar cells

Printable mesoscopic perovskite solar cells (PSCs) have shown promising prospects for practical applications due to their simple fabrication process, low material cost and high stability. The device is based on a mesoporous triple-layer scaffold, and the perovskite is deposited in the scaffold as a light absorber. Various solvents have been employed to prepare the perovskite precursors. However, the coordination between lead halides and the solvent molecules may lead to the formation of precipitates after a period of storage. The precipitates significantly influence the stoichiometric compositions of the precursors, and result in undesired variations in the device performance. Herein, we introduce ethanol (EtOH) into a typical gamma-butyrolactone (GBL) based perovskite precursor. The addition of EtOH not only weaken the coordination between Pb and solvent molecules, but also facilitate the crystallization of the perovskite absorber. Besides, the EtOH modified precursor shows improved wettability on the mesoporous scaffold, spreading and penetrating more efficiently than typical precursor. Correspondingly, highly reproducible device performance with an average power conversion efficiency (PCE) of 14.95% and best PCE of 15.11% are achieved. This work makes it possible to stabilize the perovskite precursors for a long-term period, and will significantly benefit the potential mass-production of this emerging photovoltaic technology.