Methylammonium iodide
[CAS# 14965-49-2]

Identification

• Classification: Pharmaceutical intermediate >> OLED material intermediate
• Name: Methylammonium iodide
• Synonyms: Methylamine hydroiodide
• Molecular Formula: CH₅N^.HI
• Molecular Weight: 158.97
• CAS Registry Number: 14965-49-2
• EC Number: 239-037-4
• SMILES: C[NH3+].[I-]

Properties

• Melting point: 263-265 ºC^*

^* Biltz, Heinrich; Justus Liebigs Annalen der Chemie 1921, V423, P296-300.

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H302-H315-H319-H335
• Precautionary Statements: P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H302
Specific target organ toxicity - single exposure	STOT SE	3	H335

Discovory and Applicatios

Methylammonium iodide (CH₃NH₃I, often abbreviated as MAI) is an organic-inorganic salt composed of a methylammonium cation and an iodide anion. It has attracted extensive attention in recent years due to its central role in the development of metal halide perovskite materials, which have become one of the most promising classes of semiconductors for photovoltaic and optoelectronic applications.

The history of methylammonium iodide is closely tied to the exploration of hybrid organic-inorganic perovskites. The concept of perovskite structures was known since the 19th century, but it was not until the late 20th and early 21st centuries that researchers began incorporating organic cations such as methylammonium into metal halide lattices. Methylammonium iodide was first synthesized and studied as a precursor salt for the preparation of lead halide perovskites such as CH₃NH₃PbI₃. This compound became a breakthrough material in the field of solar cells due to its excellent light-harvesting properties, tunable band gap, and relatively simple fabrication methods.

Methylammonium iodide is generally synthesized through a reaction of methylamine with hydroiodic acid. The resulting salt is purified by recrystallization, yielding a crystalline, hygroscopic solid. Its ease of synthesis and stability under ambient conditions make it a practical precursor for large-scale materials development.

The most significant application of methylammonium iodide lies in its use as the organic cation component in methylammonium lead iodide (MAPbI₃) and related mixed halide perovskites. These perovskite compounds exhibit strong light absorption, long charge-carrier diffusion lengths, and high photoluminescence quantum yields. The introduction of methylammonium iodide into these materials enabled the fabrication of perovskite solar cells with rapidly increasing efficiencies, rising from around 3% in the early 2000s to over 25% in the last decade. This exceptional progress has established methylammonium iodide-based perovskites as leading candidates for next-generation photovoltaics.

Beyond solar cells, methylammonium iodide is used in the development of light-emitting diodes (LEDs), photodetectors, and lasers based on perovskite thin films. In perovskite LEDs, the material enables bright and efficient light emission across a wide spectrum, including tunable visible and near-infrared regions. Its role in photodetectors is tied to the high absorption coefficient and fast response times of perovskite materials, while in lasing applications it contributes to high optical gain and low threshold lasing.

However, the use of methylammonium iodide also poses challenges. Perovskites containing the methylammonium cation tend to exhibit thermal and moisture instability, leading to degradation under operating conditions. The volatility of the methylammonium cation and its susceptibility to decomposition into methylamine and hydrogen iodide reduce the long-term stability of devices. As a result, research has increasingly focused on replacing methylammonium with more thermally robust cations such as formamidinium (FA⁺) or inorganic cesium (Cs⁺). Despite this, methylammonium iodide remains a key compound in perovskite research, serving as a benchmark material and playing a critical role in the historical development of the field.

In summary, methylammonium iodide is a simple yet transformative chemical substance whose incorporation into hybrid halide perovskites has revolutionized the development of photovoltaic and optoelectronic technologies. Its discovery as a suitable organic cation for perovskite structures laid the foundation for high-performance solar cells and related devices, while its limitations have motivated ongoing innovations in the design of more stable and efficient perovskite systems.

References

2025. Challenges of Preparing PSC. Synthesis Lectures on Renewable Energy Technologies.
DOI: 10.1007/978-3-031-90750-0_5

2025. Sustainable recycling of spent lead-acid batteries into perovskite thin films via inkjet printing for solar energy. International Journal of Environmental Science and Technology.
DOI: 10.1007/s13762-025-06466-6

2025. Halide perovskites for next generation electronics integrating resistive switching memory and gas sensing. Journal of the Korean Ceramic Society.
DOI: 10.1007/s43207-025-00529-7