In situ recycle of PbI2 as a step towards sustainable perovskite solar cells

The development of organometal halide perovskite solar cells has grown rapidly and the highest efficiency of the devices has recently surpassed 22%. Because these solar cells contain toxic lead, a sustainable strategy is required to prevent environmental pollution and avoid healthy hazard caused by possible lead outflow. Here, in situ recycling PbI2 from thermal decomposition CH3NH3PbI3 perovskite films for efficient perovskite solar cells was developed. The thermal behavior of CH3NH3PbI3 perovskite and its individual components were examined by thermogravimetric analysis. By optimizing the process of thermal decomposition CH3NH3PbI3 film, the complete conversion from CH3NH3PbI3 to pure PbI2 layer with a mesoporous scaffold was achieved. The mesoporous structure readily promotes the conversion efficiency of perovskite and consequently results in high-performance device. A perovskite crystal growth mechanism on the mesoporous PbI2 structure was proposed. These results suggest that in situ recycled PbI2 scaffolds can be a new route in manipulating the morphology of the perovskite active layer, providing new possibilities for high performance. Meanwhile, the risk of lead outflow can be released, and the saving-energy fabrication of efficient solar cells can be realized.