Optically Determined Hole Effective Mass in Tin-Iodide Perovskite Films

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Tin-halide perovskites are promising lead-free semiconductors for photovoltaics.
• Their charge transport is often limited by hole dominance due to self-doping.
• Understanding hole effective mass is key to optimizing performance.

Purpose of the Study:

• To develop a noncontact optical spectroscopic method for determining hole effective mass.
• To investigate the charge transport properties of FASnI3 thin films.
• To enable efficient screening of materials for improved photovoltaic applications.

Main Methods:

• Utilized mid-infrared reflectance spectroscopy on FASnI3 thin films.
• Tuned hole densities via SnF2 additive concentration and air exposure.
• Modeled plasma frequency by analyzing shifts in FA cation vibrational resonance.

Main Results:

• Accurately determined the hole effective mass in FASnI3 to be 0.28 me.
• Demonstrated valence band parabolicity within ~100 meV of the band edge.
• Observed insignificant coupling between hole plasma and FA cation.

Conclusions:

• The developed noncontact optical method is effective for characterizing hole effective mass.
• This technique facilitates the screening of tin-halide perovskites for optimized charge-carrier transport.
• The findings contribute to the advancement of lead-free photovoltaic materials.