Transfer‐Imprinting‐Assisted Growth of 2D/3D Perovskite Heterostructure Based on Organic Cations with Different Chain Lengths for Efficient Perovskite Solar Cells

2D/3D perovskite heterostructures have attracted tremendous attention and been widely used for efficient perovskite solar cells. The size of the spacer cation plays an important role in the formation of 2D perovskite layer and the device performance. Here, we compare the effect of organic cations with different chain lengths on the properties of 2D/3D perovskite heterostructures by using a transfer‐imprinting‐assisted growth (TIAG) process. It is found that the spacer cation with longer chain length (phenylbutylammonium iodide [PBAI]) is more conducive to forming 2D/3D perovskite heterojunction which can passivate the interface defects of perovskite films, compared to spacer cation with shorter chain length (phenylmethylammonium iodide [PMAI]). As a result, the power conversion efficiency (PCE) of the perovskite solar cells (PSCs) with PBAI spacer cation is improved more obviously with the champion PCE of 22.52%, compared to 20.52% of the pristine 3D perovskite device. This work demonstrates the effect of chain lengths on the formation and performance of 2D/3D perovskite heterostructures by using a solvent‐free imprinting growth process, which promotes the development of efficient 2D/3D PSCs.