Efficient p-Type Doping of Tin Halide Perovskite via Sequential Diffusion for Thermoelectrics

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Metal halide perovskites (MHPs) possess favorable thermoelectric properties due to their unique lattice structures.
• Poor electrical conductivity in lead-based MHPs (<10¹⁴ cm^-3) hinders their thermoelectric (TE) application.
• Tin halide perovskites (THPs) offer high intrinsic hole densities (>10¹⁹ cm^-3) but face doping challenges.

Purpose of the Study:

• To develop an effective doping strategy for tin halide perovskites (THPs) to enhance their thermoelectric performance.
• To overcome the limitations of accommodating dopants and heavy compensation in THPs.
• To investigate the impact of a novel diffusion-mediated doping approach on THP electrical and thermal conductivity.

Main Methods:

• A diffusion-mediated doping approach involving air exposure and surface treatment with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F₄TCNQ).
• Application of the doping method to the photovoltaic tin halide perovskite, CH(NH₂)₂SnI₃ (FASnI₃) thin films.
• Characterization of electrical conductivity, thermal conductivity, and power factor before and after doping.

Main Results:

• Electrical conductivity of FASnI₃ thin films increased dramatically by 300×, from 0.06 to 18 S cm^-1.
• The power factor was enhanced by 25×, reaching 53 μW m^-1 K^-2.
• Thermal conductivity showed minimal change, indicating the lattice structure remained intact after doping.

Conclusions:

• The demonstrated diffusion-mediated doping approach effectively enhances the p-type doping level in THPs.
• This method significantly improves the thermoelectric performance of tin halide perovskites, particularly the power factor.
• The findings provide a promising pathway for advancing thermoelectric applications of halide perovskites.