Hall effect is among the most fundamental effects in physics and plays important role in semiconductor R&D. It tells us the most fundamental information of the majority charge carriers in semiconductor: their type (P or N), density (n) and mobility (μ). Consider an electronic material under light illumination such as a solar cell absorber that has both majority and minority carriers. Until recently, we did not know how to extract both carrier information such as mobility and density simultaneously. This information have been buried in the photo-Hall measurement and unknown since the discovery of the Hall effect in 1879. We present an exciting discovery of a new insight in the photo-Hall effect which can be expressed as: ΔμH = d(σ2H)/dσ where ΔμH is the hole and electron Hall mobility difference, σ is the conductivity and H is the Hall coefficient. This equation allows us to extract both majority and minority carrier information simultaneously and unlocks an astonishing array of charge carrier parameters such as their mobility, photo-carrier density, recombination lifetime, diffusion lengths and recombination coefficients. The experiment is enabled by new advances in high sensitivity ac Hall measurement using a parallel dipole line system. We applied this technique in high performance perovskite and kesterite solar cell films, demonstrating a new exciting capability of characterizing semiconductor materials with unprecedented details. We will also share some behind-the-screen story of this discovery at IBM Research.

Carrier-resolved photo-hall effect: 140-year-old secret in hall effect

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.