Reassessing the Validity of Space-Charge-Limited Current Measurements in Perovskite Devices with Charge-Transporting Layers: A Drift-Diffusion Simulation Including Charge Transition Levels

Space-charge-limited current (SCLC) analysis is widely employed to extract trap densities and carrier mobility in perovskite materials. However, its validity in multilayer perovskite devices, such as those incorporating charge-transporting layers (CTLs), has remained insufficiently examined. Moreover, coupled electronic-ionic charge transport in perovskite materials, where mobile ions act as free carrier traps, remains incompletely understood. In this work, we critically reassess the applicability of SCLC measurements in multilayer perovskite devices. We develop a physics-based drift-diffusion model that explicitly incorporates ionic trap dynamics with charge transition levels, accounting for the unique ionic and electronic behaviors of halide perovskites. Through comparison between theoretical simulations and experimental SCLC data using a prebias and rapid forward-scan technique to decouple ionic and electronic contributions, our drift-diffusion model reveals that the SCLC response is dominated by the CTLs─particularly Spiro-OMeTAD─rather than by traps within the perovskite layer itself. At low perovskite ion densities, the minimum resolvable trap density is determined by Spiro-OMeTAD, while at high ion densities, space-charge effects are dominated by electric field screening from readily filled iodide interstitials rather than by trapping processes. Mobility values extracted from the high-voltage regime closely align with the CTL mobility, not with that of the perovskite. These findings highlight the fundamental limitations of conventional SCLC analysis in multilayer perovskite device architectures and underscore the need for revised frameworks to accurately characterize perovskite-based devices.