Formamidinium Iodide (FAI), with CAS number 879643-71-7, is a critical material driving innovation in the solar energy sector, particularly in the development of high-efficiency perovskite solar cells (PSCs). Its superior properties, such as a favorable band gap and better environmental stability compared to earlier materials like methylammonium lead iodide (MAPbI3), have made it a preferred choice for researchers aiming to push the boundaries of solar energy conversion. The success of formamidinium iodide perovskite solar cells is largely attributed to these advancements.

A fundamental challenge associated with FAI is the inherent instability of its desired black phase, α-FAPbI3. This phase, vital for efficient light absorption and charge transport, can easily convert to the inactive yellow δ-FAPbI3 phase. This instability poses a significant obstacle to achieving long-term operational durability, making stabilizing the alpha-FAPbI3 phase a paramount goal in the field.

To address this, scientists are employing a range of sophisticated techniques. Defect control in FAPbI3 is one such critical area. By minimizing structural imperfections, such as vacancies and interstitials, the intrinsic stability of the perovskite lattice can be enhanced, thereby hindering the phase transition. This requires precise control over the synthesis and processing conditions.

Another key strategy is composition engineering for perovskites. This involves strategically altering the chemical makeup of the perovskite material to improve its robustness. Research into A-site doping for perovskites and B-site doping in FAPbI3 is particularly active. For instance, incorporating smaller cations like cesium (Cs) or specific lanthanide ions, as highlighted in studies on lanthanide ion doping perovskite materials, can modify the lattice parameters and strengthen the material's resistance to degradation.

Understanding the mechanisms behind perovskite solar cell degradation is crucial for devising effective stabilization methods. Scientific investigations are continuously revealing new insights into how environmental factors and intrinsic material properties influence stability. This deep understanding of lead halide perovskite stability is essential for designing next-generation solar technologies.

The broad range of formamidinium lead iodide applications underscores its importance in advanced energy materials. As research continues to refine synthesis methods and stabilization techniques, FAI is set to play an even more significant role in making solar energy more accessible and efficient. The ongoing quest for stable FAI is a vital step towards a sustainable energy future.