FAPbX3

FAPbX3 refers to a family of lead halide perovskites in which the organic cation formamidinium (FA+) occupies the A-site of the ABX3 lattice, with B = lead (Pb2+) and X = halide (I−, Br−, or Cl−). They crystallize in a three-dimensional network built from corner-sharing PbX6 octahedra and are studied for optoelectronic applications due to strong light absorption and favorable charge-transport properties.

Formulations include FAPbI3, FAPbBr3, FAPbCl3, and mixed-halide variants such as FAPb(I1−xBrx)3. The halide composition tunes the bandgap and optical response, enabling absorption across a broad range of energies from near-infrared to near-UV. The alpha-phase of FAPbI3 is the desirable black, photoactive form, but at room temperature it tends to transform into a yellow non-perovskite delta phase, which reduces performance and stability. Mixed-halide and mixed-cation strategies are used to mitigate this issue.

Stability improvements are pursued through cation engineering (for example, incorporating cesium or methylammonium alongside formamidinium), halide mixing, and the use of 3D-2D or quasi-2D architectures, as well as additives and optimized processing to enhance film quality and suppress phase transitions. These approaches aim to produce durable, high-performance devices.

Applications and challenges: FAPbX3-based perovskites are central to high-efficiency thin-film solar cells and light-emitting diodes, but long-term stability, moisture sensitivity, thermal stability, and concerns about lead content remain active areas of research. Continuous development focuses on understanding degradation mechanisms and scaling production while addressing environmental considerations.