Surface Defects Control Bulk Carrier Densities in Polycrystalline Pb-Halide Perovskites

Area of Science:

• Materials Science
• Solid-State Physics
• Optoelectronics

Background:

• Semiconductor optoelectronic properties are dictated by free carrier densities, typically regulated by doping.
• Metal halide perovskites (HaPs) are promising functional materials, yet their unique properties challenge conventional semiconductor understanding.

Purpose of the Study:

• To investigate the primary factors controlling doping type and density in lead-based metal halide perovskites (Pb-HaPs).
• To elucidate the role of surfaces and interfaces in the optoelectronic behavior of HaP devices.

Main Methods:

• Analysis of carrier densities in polycrystalline Pb-HaP films.
• Assessment of the impact of surface sites on electrical activity.
• Evaluation of interfacial defect roles in multi-layered device structures.

Main Results:

• For Pb-HaPs, surface sites, rather than bulk doping, predominantly control carrier densities.
• Electrically active surface defects significantly influence optoelectronic properties, even at low densities.
• Interfacial defects are critical in multi-layered HaP devices.

Conclusions:

• Surface and interface passivation are paramount for controlling Pb-HaP optoelectronic characteristics.
• The difficulty in bulk doping HaPs makes surface effects critically dominant.
• Understanding surface control is essential for advancing HaP-based technologies.