Enabling room-temperature processed highly efficient and stable 2D Ruddlesden-Popper perovskite solar cells with eliminated hysteresis by synergistic exploitation of additives and solvents

Herein we demonstrate the favorable synergistic effect of an NH₄Cl additive and DMSO solvent on 2D perovskites that are synthesized at room temperature. Interestingly, we observe the spontaneous formation of 3D phases within either NH₄Cl or DMSO treated 2D perovskites, which plays a pivotal role in facilitating charge transport. It is revealed that NH₄Cl increases charge carrier lifetime and passivate trap states within the 3D phase while DMSO promotes 2D/3D inter-phase charge transfer. These two competitive processes reach a delicate balance in DMSO and NH₄Cl co-treated devices, which deliver a maximum PCE up to 13.41% with excellent air-stability and eliminated hysteresis. This is among the highest values reported for 2D RP perovskite (n = 4) based planar solar cells, particularly via all low-temperature solution fabrication.