CH3NH3PbI3

CH3NH3PbI3, also written as methylammonium lead iodide, is an organometal halide perovskite with the chemical formula ABX3, where A = methylammonium (CH3NH3+), B = lead (Pb2+), and X = iodide. In the solid state it adopts the perovskite structure, with a three-dimensional network of corner-sharing PbI6 octahedra and A-site cations occupying cuboctahedral cavities. At room temperature it typically exists in a tetragonal phase and transitions to cubic at higher temperatures.

Optical and electronic properties: It has a direct bandgap around 1.55 eV and strong light absorption, enabling high short-circuit currents in thin films. The material can be solution-processed from common solvents, allowing simple fabrication.

Applications: It is a leading absorber layer in perovskite solar cells, often part of architectures such as mesoporous TiO2 or planar heterojunctions, with transport layers for electrons and holes. Laboratory devices have achieved power conversion efficiencies exceeding 25%, with rapid progress since its first demonstration in 2009.

Stability and challenges: The material is sensitive to moisture, heat, and UV light, which affects long-term stability. Efforts include compositional engineering (e.g., mixed cations or halides), film processing optimization, and encapsulation. Lead content raises concerns about environmental and biohazard risks, driving research into lead-free perovskites or recycling strategies.

Synthesis and properties: typical synthesis involves reacting methylammonium iodide with lead iodide in polar aprotic solvents, followed by slow crystallization; properties can be tuned by halide composition and cation selection. The material is compatible with various device architectures and is a major focus of photovoltaic research.

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