Terahertz optical Hall effect determination of carrier concentrations in component layers within low bandgap tin–lead halide perovskite photovoltaics and device simulation

Abstract

Carrier concentration (N) of indium tin oxide (ITO), poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), and low bandgap perovskite (FASnI3)0.6(MAPbI3)0.4 in the photovoltaic device configuration are determined using terahertz (THz) spectral range optical Hall effect measurements and analysis. Unlike direct electrical Hall effect, this technique is non-invasive as it does not need any direct electrical contacts and is able to probe free carrier transport properties of individual films inside the device stack. A modified Drude model is implemented to address the dominating free carrier absorption in the THz spectral range. N of the ITO, PEDOT:PSS, and (FASnI3)0.6(MAPbI3)0.4 are determined to be (2.8 ± 0.6) × 1020 cm-3, (2.6 ± 0.8) × 1022 cm-3, and (1.5 ± 0.1) × 1018 cm-3, respectively. PV device performance is simulated with SCAPS employing the findings from optical Hall measurements. Open circuit voltage (VOC), short circuit current (JSC), fill factor (FF), power conversion efficiency (PCE) are found to be 0.865 V, 29.2 mAcm-2, 66.7%, and 16.8% respectively which are within 3% of corresponding experimentally measured values. These optically measured N serve as essential parameters for device modeling to understand its physics in device performance and to optimize PCE; consistency between simulated and experimental device performance parameters using these values supports optical Hall effect as a reliable technique to extract electronic transport properties.