Nowadays, silicon-based photovoltaic (PV) panels that directly convert sunlight into electricity have been commercially available for both individual buildings and small-scale power plants. However, the production of crystalline silicon PV modules consumes a lot of energy and fossil fuels, thus the whole life cycle of silicon solar cells is not as green as you think. Therefore, researchers have been exploring low-cost and energy-efficient non-silicon-based PV technologies for decades, among which the halide perovskitebased PV quickly stood out and has attracted tremendous research efforts due to its simple solution-based fabrication and competitive power conversion efficiency (PCE). Pioneered by Prof. Tsutomu Miyasaka and colleagues from Toin University of Yokohama in Japan in 2009, [1,2] the labscale halide perovskite PV device has witnessed a PCE enhancement from 3.8% to above 20%, which is comparable to silicon, during just one decade.Currently, the commercialization of halide perovskite solar cells is hindered by two profound issues. [2] The first obstacle is the long-term instability under operational conditions involving atmospheric moisture, raised temperature, and real sunlight. For example, CH3NH3PbI3, a typical high-efficiency perovskite PV material, degrades easily at 120 ℃. [2] Second, the high-efficiency perovskites contain the toxic lead element, which can potentially harm the environment and human health and thus has been a major concern for commercialization. Many efforts have been devoted to addressing these issues. Especially, the compositional tuning of the perovskites, like the mixing of cations and anions, has led to remarkable improvements. At present, further research in the direction of compositional engineering is urgently desired to balance the stability, efficiency, and toxicity issues of perovskites.