Tackling Challenges in Seebeck Coefficient Measurement of Ultra-High Resistance Samples with an AC Technique

TL;DR

This paper introduces an AC measurement technique enabling accurate Seebeck coefficient determination for ultra-high resistance samples, exemplified by a novel measurement on CH3NH3PbI3 perovskite.

Contribution

The study presents a new AC-based method for measuring Seebeck coefficients in samples with resistances up to 100 GΩ, overcoming limitations of traditional DC techniques.

Findings

Measured Seebeck coefficient of CH3NH3PbI3 at +550 μV/K

Demonstrated high resistance measurement up to 100 GΩ

Enabled study of previously unmeasurable high-resistance materials

Abstract

Seebeck coefficient is a widely-studied semiconductor property. Conventional Seebeck coefficient measurements are based on DC voltage measurement. Normally this is performed on samples with low resistances below a few Mohm level. Meanwhile, certain semiconductors are highly intrinsic and resistive, many examples can be found in optical and photovoltaic materials. The hybrid halide perovskites that have gained extensive attention recently are a good example. Few credible studies exist on the Seebeck coefficient of, CH3NH3PbI3, for example. We report here an AC technique based Seebeck coefficient measurement, which makes high quality voltage measurement on samples with resistances up to 100Gohm. This is achieved through a specifically designed setup to enhance sample isolation and reduce meter loading. As a demonstration, we performed Seebeck coefficient measurement of a CH3NH3PbI3 thin film at dark and found S = +550 microV/K. Such property of this material has not been successfully studied before.