inexhaustible features. It is well known that solar cells can absorb photons from sunlight, resulting in electron-hole pairs, which would be segmented by the built-in electric field at the interface of two different semiconductors. As a result, the electric current would be produced and the solar energy is converted to electric energy. Up to now, the development of solar cells can be roughly categorized into four types based on their basic forming materials. For the first type, solar cells are mostly made of single crystal silicon, polycrystalline silicon, and noncrystalline silicon. The configuration of these cells is normally based on the p-i-n junction, showing a superior photoelectrical conversion efficiency (PCE) up to about 25.6% (Panasonic, Japan). [33] However, the manufacturing cost is very high due to complicated crafting and high purity demand. Furthermore, the by-product of silicon is hazardous to the environment. Scientists thereby keep looking for alternatives that can offer even better efficiency and are environmentally friendly. The second type refers to the inorganic solar cells that are made of CdS, CdTe, GaAs, and CuIn(Ga)Se films. The highest PCE of such type of cells were reported to be 21.7% (ZSW, Germany). [33] Although this value is close to the performance of Si-based solar cells, the use of rare elements (Ga, Te, Se) and highly toxic Cd makes it to be hard for further developments. The third type of solar cells are the organic photovoltaic cells (OPCs), which are made of magnesium phthalocyanine (MgPc)-based materials, in which the electron-hole pairs are stimulated by the organic p-i-n junction, giving the PCE of about ≈10.6%. [34] In addition to this unsatisfactory PCE, OPCs were also reported to have a short lifetime due to their poor stability. The fourth type of solar cells is the dye-sensitized solar cells (DSSCs), which are typically consisted of organic dyes, TiO 2 electron absorber layer, and I − /I 3 − -based liquid electrolyte. The highest PCE of DSSCs only reach about 13%, [35] and the leakage of liquid electrolyte is still unsolved. By considering all the factors mentioned above, currently, the Si-based solar cells still dominate the market over the other three types.Recently, the emerging organic-inorganic metal halide perovskite (CH 3 NH 3 PbI 3 ) solar cells (PSCs) have challenged this monopoly status. Owing to the strong absorption coefficient, long charge diffusion length, fast charge migration rate, and small excitation binding energy (50 meV), the PCE of PSCs has been recently enhanced from 3.8% to 22.1%, [36] In recent years, organic-inorganic halide perovskites have emerged as prospective materials for high-efficiency, inexpensive, and environmentally friendly perovskite solar cells (PSCs). Despite their superiority in synthesizing route, the poor stability of PSCs with regard to humidity, heat, UV radiation, and oxygen limits their applications. Moreover, the toxicity of perovskite films and suitable ways to achieve large-area production need to be taken into accou...