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Complexities of Contact Potential Difference Measurements on Metal Halide Perovskite Surfaces
Fengyu Zhang1, Florian Ullrich2, Scott Silver1
1Department of Electrical Engineering , Princeton University , Princeton , New Jersey 08544 , United States.
The Journal of Physical Chemistry Letters
|February 12, 2019
Summary
Investigating metal halide perovskite (MHP) surfaces with Kelvin probe methods reveals that light can alter surface potential by releasing halides. Monitoring probe work function is crucial to avoid misinterpreting MHP surface energetics.
Area of Science:
- Materials Science
- Surface Science
- Photovoltaics
Background:
- Metal halide perovskites (MHPs) are promising for optoelectronic devices.
- Understanding MHP surface stability and energetics is critical for device performance.
- Previous studies often overlook dynamic surface changes under illumination.
Purpose of the Study:
- To investigate the surface potential and photoresponse of methylammonium lead bromide (MAPbBr3) and butylammonium lead iodide (BA2PbI4) films.
- To identify potential artifacts in Kelvin probe measurements of MHPs.
- To highlight the importance of monitoring probe work function during MHP surface analysis.
Main Methods:
- Vacuum-based Kelvin probe measurements of contact potential difference.
- Surface photovoltage (SPV) measurements under supraband gap light irradiation.
- Analysis of halide species adsorption on the Kelvin probe tip.
Main Results:
- Supraband gap light irradiation induces halide loss from MHP surfaces.
- Adsorbed halides cause quasi-irreversible changes in MHP and probe work functions.
- These changes can lead to misinterpretation of MHP surface potential if not accounted for.
Conclusions:
- Kelvin probe techniques provide valuable insights into perovskite surface energetics.
- Uncontrolled halide desorption and adsorption can significantly affect measurements.
- Continuous monitoring of probe work function is essential for accurate MHP surface characterization.
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