Impact of metal halide perovskite dimensionality on 1-propanol gas sensing

Detection of harmful gases and volatile organic compounds (VOCs) is significant for safety and product assessment. Among detecting gases like H₂S or NO₂, a typical example of VOCs sensing is the breath alcohol concentration to prevent impaired driving. Materials used in gas sensors for volatile organic compounds are dominated by metal oxides (MO), which must be heated to 150 - 500 ℃ to gain high sensitivity. Metal oxides need high temperatures to undergo a redox reaction between the VOC and the MO surface. Metal halide perovskites do not need high temperatures because the analyte adsorbs on the surface and thereby passivates surface defects. This passivation decreases the resistance of the perovskite.

Here we show that lead bromide perovskites can be used for 1-propanol detection at room temperature. We evaluated two different compositions that result in 2D and 3D metal halide films, namely, phenylethylammonium lead bromide ((PEA)₂PbBr₄) and methylammonium lead bromide (MAPbBr₃), respectively. By placing a thin film of perovskite with top electrodes in a constant flow of 1-propanol vapor, the conductivity of (PEA)₂PbBr₄ increases by 10⁷, whereas the 3D phase showed only an increase of 10⁴ at 7000 ppm. Interestingly, the gas sensors are reusable. We characterize the surface and structure of our films employing electron microscopy, atomic force microscopy, and GIWAXs. Although the 3D phase has a larger surface area than the 2D phase, due to the smaller grain size the increase in conductivity is much greater with the 2D phase, which indicates a larger number of surface defects. Also, the defects in the 2D perovskites are energetically deeper and, when passivated by the alcohol, increase the film’s conductivity much more than in the case of the 3D perovskite, which is in agreement with DFT calculations on the defect energetics of the two systems.¹ Our work demonstrates that metal halide perovskite can work as efficient VOC gas sensors² displaying room temperature operation and low power consumption.

References:

1)Simon Kahmann, Daniele Meggiolaro, Luca Gregori, Eelco K. Tekelenburg, Matteo Pitaro, Samuel D. Stranks, Filippo De Angelis, and Maria A. Loi, ACS Energy Letters 2022 7 (12), 4232-4241, DOI: 10.1021/acsenergylett.2c02123

2)Paul Hänsch, Maria A. Loi; Metal halide perovskites: A rising platform for gas sensing?. Appl. Phys. Lett.17 July 2023; 123 (3): 030501. https://doi.org/10.1063/5.0151942