Stabilization of Polymorphic Halide Perovskite Black Phase for Optoelectronic Applications

The photovoltaic and luminance efficiencies of halide perovskite-based devices achieved an unprecedented improvement in comparison to their existing counterparts. Among the family of lead-based halide perovskites, the formamidinium lead iodide (FAPbI3) and cesium lead iodide (CsPbI3) systems are especially interesting in the occurrence of low bandgap nature to the former and high thermal stability to the latter class of material. However, the room temperature polymorphic behaviour and the existence of the non-photoactive phase curbs the potentiality of these halide perovskites in efficient and stable optoelectronic devices. In this aspect, our study revealed the phase stability of polymorphic FAPbI3 halide perovskite by benefitting the diversity of the embedded PbS QDs additive in terms of chemical and structural traits for manipulating the morphological, structural, and black phase stability of the blended FAPbI3 system. In addition, our work illustrates the benefits of the low-cost ambient atmospheric fabrication for the formation of efficient and stable polymorphic FAPbI3 halide perovskite thin films and solar cells. Finally, it is pointed out the necessity of balanced charge carrier injection in CsPbI3 QDs PeLEDs by carefully choosing the quality of emissive material and suitable interfacial charge transport layers for the efficiency and stability of the devices.