Insights from Impedance Spectroscopy in Perovskite Solar Cells with Self-Assembled Monolayers: Decoding SAM’s Tricks
Clara Aranda, Wenhui Li, Eugenia Martínez‐Ferrero, Paul Pistor, Gerko Oskam, Emilio Palomares, Juan A. Anta
Abstract
Self-assembled monolayers (SAMs) are highly promising hole-transport layers for p-i-n perovskite solar cells, increasing photocurrent, reducing hysteresis and boosting photovoltage. However, the SAM’s exact role in maintaining those benefits remains elusive. This work demonstrates that SAMs enhance open-circuit voltage ( V oc ) and stability by suppressing surface recombination, as revealed by impedance spectroscopy. This is reflected in the time constants related to ionic dynamics, taking values from 10 –2 to 10 –1 s for PTAA-based samples and 10 –3 s for SAM devices. X-ray photoelectron spectroscopy shows that SAMs chemically bind with hydroxyl groups on metal oxide substrates such as indium tin oxide, reducing ionic accumulation and preventing ion-induced V oc losses. With minimal ionic dynamics, SAM-based devices achieve outstanding photovoltage and stability, confirming SAMs as pivotal in advancing perovskite cell performance.