Revealing Charge Carrier Mobility and Defect Densities in Metal Halide Perovskites via Space-Charge-Limited Current Measurements

TLDR

SCLC measurements are commonly used to probe carrier mobility and trap density in semiconductors, but their application to metal halide perovskites is complicated by the materials’ mixed ionic and electronic behavior. The study aims to identify the limitations of conventional SCLC in perovskites caused by mobile ions and to propose pulsed SCLC as a more reliable approach. The authors employ drift‑diffusion simulations and pulsed SCLC measurements, combining them to refine analysis and simultaneously extract mobility, trap, and ion densities. Classical SCLC methods cannot directly quantify trap density or mobility, but the refined pulsed SCLC approach yields a trap density of 1.3×10¹³ cm⁻³, an ion density of 1.1×10¹³ cm⁻³, and a mobility of 13 cm² V⁻¹ s⁻¹ in a MAPbBr₃ single crystal.

Abstract

Space-charge-limited current (SCLC) measurements have been widely used to study the charge carrier mobility and trap density in semiconductors. However, their applicability to metal halide perovskites is not straightforward, due to the mixed ionic and electronic nature of these materials. Here, we discuss the pitfalls of SCLC for perovskite semiconductors, and especially the effect of mobile ions. We show, using drift-diffusion (DD) simulations, that the ions strongly affect the measurement and that the usual analysis and interpretation of SCLC need to be refined. We highlight that the trap density and mobility cannot be directly quantified using classical methods. We discuss the advantages of pulsed SCLC for obtaining reliable data with minimal influence of the ionic motion. We then show that fitting the pulsed SCLC with DD modeling is a reliable method for extracting mobility, trap, and ion densities simultaneously. As a proof of concept, we obtain a trap density of 1.3 × 1013 cm–3, an ion density of 1.1 × 1013 cm–3, and a mobility of 13 cm2 V–1 s–1 for a MAPbBr3 single crystal.