Whether organic spacer cations induced 2D/3D or quasi-2D/3D mixed dimensional perovskites?

Abstract

The dimensional engineering of perovskite films has been demonstrated to be an efficient technique to enhance both the efficiency and stability of perovskite solar cells (PSCs). Whether the alternative spacer cations induced 2D/3D or quasi-2D/3D mixed dimensional perovskites make a great difference in the photovoltaic performance and their stability of corresponding PSCs. But the research on this aspect is still insufficient, the crystal structure of the mixed dimensional perovskite is still unclear, which needs more in-depth research. This work adopted the alternative spacer cation of 4-(aminoethyl) pyridine (4-AEP) and the conventional phenylethylamine (PEA), to study their induced low-dimensional crystal phase in 3D perovskite and compare the effect on the performance of corresponding PSCs. We demonstrated that 4-AEP cation has induced 2D crystal phase (low n-value) at the 3D grain boundaries, while the PEA has induced quasi-2D (high n-value) one. As a result, the 4-AEP incorporated MAPbI3 (2D/3D) PSCs obtained a higher power conversion efficiency (PCE, 20.7%) than that of the PEA based quasi-2D/3D ones. More importantly, the 4-AEP based 2D/3D PSCs exhibited better moisture resistance and long-term stability when exposed to moisture and continuous light irradiation. Our work demonstrated that the alternative organic spacer cation could induce 2D or quasi-2D phase in 3D perovskite, but the 2D/3D mixed dimensional perovskite shows more favorable for obtaining highly efficient and stable perovskite solar cells.