Lattice Strain Relaxation and Grain Homogenization for Efficient Inverted MAPbI₃ Perovskite Solar Cells

The lattice strain of a perovskite film is vital to the controllable growth and charge transport in perovskite solar cells (PSCs). In this work, a lead chloride (PbCl₂) assisted crystallization (LCAC) protocol is introduced for releasing the strain across the interface of a NiO/perovskite, which induces a preferred (h00) crystal plane growth and grain homogenization. PSCs with LCAC show a facilitated charge extraction and suppressed nonradiative recombination. Thanks to the controlled film growth and strain-released interface, the inverted MAPbI₃ (MA = methylammonium) PSC devices with LCAC deliver a power conversion efficiency (PCE) over 20% with a short-circuit current density (J_sc) of 23.60 mA cm^-2, which is obviously higher than that of the control device with a PCE of 18.36% and a J_sc of 21.74 mA cm^-2. Meanwhile, the LCAC devices maintain 80% of their initial efficiency after being exposed to an ambient atmosphere with a relative humidity of 40% over 1000 h in the dark.