Time- and Space-Resolved Characterization of Carrier Dynamics and Defect Evolution in Photovoltaic Devices Using Transient Techniques.

Abstract

The spatiotemporal interplay between carrier dynamics and defect evolution critically determines solar cell performance yet is often obscured by the limitations of conventional characterization methods. Here, an integrated transient photovoltage (TPV) and photocurrent (TPC) mapping system are presented to diagnose complex defect physics in photovoltaic devices. For Passivated Emitter Rear Cell (PERC) solar cells with artificial surface recombination, a novel analytical framework is demonstrated to visualize defects, overcoming the single-point limitation of conventional transient methods. While conventional lifetime mapping proves insensitive to localized defects due to spatial-averaging effects, whereas a map of the TPV fit variance, which probes local kinetic complexity, serves as a powerful and direct indicator of recombination-active defect zones. In studying the light-induced degradation (LID) of GaAs solar cells, the paradox of power conversion efficiency is resolved, decreasing from 24.45% to 22.45% despite a counterintuitive increase in photoluminescence. An evidence is provided for a light-induced modification of key interfaces, where enhanced electron accumulation elevates the internal carrier population (increasing PL), while a concurrently formed barrier to charge extraction at the contacts degrades overall device performance. This work presents a powerful methodology for moving beyond simple defect mapping to a more profound, mechanism-based understanding of device performance and stability.