Metal Halide Perovskite Thin Film Optical Properties Following H₂ Exposure— Implications for Gas Sensors

Hydrogen gas (H₂) has emerged as a promising solution to climate change challenges, offering a clean, versatile energy source that produces only water vapor upon use. While H₂ itself is not a greenhouse gas (GHG), its environmental interactions can indirectly influence GHG levels, highlighting the importance of optimal H₂ utilization in mitigating climate change. As H₂ becomes more prevalent in energy systems, transportation, and industrial processes, the need for efficient and reliable H₂ detection methods grows increasingly critical. Accurate H₂ sensing is essential for safety in storage and transport, optimizing fuel cell performance, and preventing leaks that could lead to economic losses or potential hazards. Furthermore, precise H₂ detection can enhance the efficiency of hydrogen production processes, such as water electrolysis, contributing to the overall effectiveness of hydrogen as a sustainable energy carrier.
Metal Halide Perovskite (MHP) thin films, renowned for their exceptional optical and electronic properties, have found applications in photovoltaics, LEDs, luminescent solar concentrators, lasers and photodetectors. Recently, MHPs have shown potential as environmental gas sensors. Our research focuses on characterizing the interaction between CH₃NH₃PbI₃ (methylammonium lead iodide or MAPI) thin films and H₂ for potential use in optical H₂ sensing.
Using photoluminescence spectroscopy (PL), we observed an initial increase in MAPI emission intensity upon H₂ exposure, followed by a gradual quenching below the baseline. This repeatable response indicates promising sensor capabilities. Similarly, charge carrier recombination lifetimes initially lengthened before returning to baseline. The magnitude of these responses correlated with H₂ concentration, suggesting potential for quantitative sensing. X-ray diffraction confirmed MAPI's structural stability post-H₂ exposure.
Additionally, we investigated the interaction between a mixed halide perovskite (CH₃NH₃PbI_3-xCl_x) and H₂ to elucidate the sensing mechanism, which appears to involve electron release upon H₂ bonding at the MHP halide sites. Film thickness was also varied, with thinner films showing a reduced response, indicating that the reaction was not limited to the film surface but occurred throughout the bulk of the material.
This research contributes to the development of novel, highly sensitive H₂ sensors based on MHP compunds. Such sensors could play a crucial role in the safe and efficient implementation of hydrogen technologies across various sectors, supporting the transition to a low-carbon economy and advancing efforts to combat climate change.
The authors acknowledge funding from NSF grant no.DGE-2125510.