Uncovering the Role of Guanidinium in Enhancing Charge Extraction in p-i-n Perovskite Solar Cells

Guanidinium cation (GA) has been reported to improve the optoelectronic properties and performance of lead halide perovskite solar cells (PSC). While most previous work has focused on n-i-p structured PSCs, the role of GA alloying in the p-i-n structure has been less explored. This study comprehensively investigated the impact of partial cation substitution by GA in perovskite materials on their optoelectronic properties, device efficiency, stability, and charge carrier dynamics.

Our findings reveal that improved power conversion efficiency is primarily due to significant enhancements in short-circuit current density and fill factor values, with no notable change in open-circuit voltage. Additionally, devices incorporating GA demonstrate improved operational stability. Spectroscopic and microscopic analyses suggest that these improvements are mainly due to the reduction of localized sub-micrometre inhomogeneities after GA incorporation, which enhances charge transport properties and light stability in the perovskite materials and, consequently, the overall charge extraction efficiency and stability devices.

Our observations provide a comprehensive and deep understanding of the role of GA in materials and device engineering for p-i-n PSCs, highlighting a different mechanism from that observed in n-i-p PSCs, where performance enhancement is primarily attributed to trap state reduction, resulting in higher open-circuit voltage.