The energy demand is rapidly increasing for the increased population and the improved life quality. [1] Disafforestation or mining will destroy the ecological balance and even bring some unknown diseases, which will kill thousands of people. Thus, an environmentally friendly method to obtain energy is necessary and urgent. Solar energy is a kind of clean and abundant energy, which can be harvested conveniently. Nowadays, silicon solar cells are dominant in the solar energy industry, but we need more cost-effective solar energy. [2] The 3D perovskite solar cell (PSC) is a low-cost photovoltaic research frontier for its roaring increase in power conversion efficiency (PCE) from 3.8% in 2009 to 25.2% in 2019 because the perovskite shows the excellent optoelectronic properties, including the large absorption coefficient, the small exciton binding energy, and the considerable carrier diffusion length. [3] However, the stability of PSC remains some distance ahead of the industrial application. [4] Therefore, the 2D perovskite can be introduced to protect the 3D perovskite, which not only keeps the high PCE but also improves the stability. Suitable alignment of the energy level in the heterojunction is vital to transfer charges and block the hole-electron recombination in the device, which can achieve better photovoltaic performance. [5] The 2D perovskite can form a wide-bandgap layer, [6] promote the hole extraction, hinder the electron transfer, and reduce the hole-electron recombination. [7] Moreover, the 2D perovskite is hydrophobic and stable under illumination, promoting the humidity and illumination stability of PSC. [8]