High-sensitivity rotating parallel dipole line hall system for photovoltaic research: Characteristics and application examples in high performance kesterite and perovskite
Many emerging solar absorbers are polycrystalline films with low mobility or very high resistance. This makes standard (dc) Hall measurement very difficult or impossible - yet the information of carrier density, type and mobility are critically needed to understand and optimize device performance. We have developed a high-sensitivity Hall measurement system based on a rotating parallel dipole line (PDL) magnet - a new magnetic trap system recently developed at IBM [1,2]. The system produces strong (up to 2 Tpk-pk), unidirectional and oscillating magnetic field that allows detection of small Hall signal in the Fourier domain followed by lock-in detection. We describe the experimental setup, operation characteristics and some application examples in the development of IBM high performance kesterite (CZTSSe) with device efficiency (η) up to 12%  and high performance perovskite from Korea Research Institute of Chemical Technology (KRICT, up to 19%) .