Exploring interfacial charge dynamics in (GPA) 2 (MA) 4 Pb 5 I16-based perovskite solar cells: Device optimization and impedance spectroscopy analysis

The organic spacer deployment in low-dimensional Ruddlesden–Popper (LDRP) perovskite (PVT) solar cells (PSCs) is exceptionally pioneering, attributed to fortified device stability and scalability. However, the recognition of optimal spacer molecules persists as an intangible challenge. Therefore, this work scrutinizes 3-guanidinopropanoic acid (GPA) as a transformative bulky organic spacer promising robust hydrogen bonding and superior interfacial passivation, ensuring stable and productive PSCs. To comply with existing demands for commercially viable and ambient-stable PSCs, the work explores a detailed numerical simulation of an efficient GPA-based LDRP system, (GPA) 2 (MA) 4 Pb 5 I[Formula: see text]. Extensive optimization of absorber thickness, acceptor concentration, effective density of states, interface defect density, and electron transport layer (ETL) electron affinity led to a peak power conversion efficiency (PCE) of 20.95%, an open-circuit voltage ([Formula: see text]) of 1.145[Formula: see text]V, a short-circuit current density ([Formula: see text]) of 24.18[Formula: see text]mA/cm 2 , and a fill factor (FF) of 73.38%. A detailed interpretation of electrochemical impedance spectroscopy (EIS) proves a minimum series resistance and charge transfer resistance of 31.27[Formula: see text] [Formula: see text] and 790.92[Formula: see text] [Formula: see text], respectively, at the intermediate absorber thickness regime (600–900[Formula: see text]nm), affirming thickness optimality. The optimization on interface engineering identified an ideal ETL electron affinity of 3.6[Formula: see text]eV, enabling efficient charge extraction and a minimal recombination rate ([Formula: see text] [Formula: see text]cm[Formula: see text] [Formula: see text]s[Formula: see text]). Moreover, EIS analysis using an appropriate equivalent circuit validated the interfacial charge-transport characteristics, while comparative evaluation of different ETL/HTL combinations established the optimum device architecture with superior photovoltaic performance. The extensive validation on band alignment, recombination profile, and current density–voltage analysis affirms GPA’s productiveness on unencapsulated operational stability while serving as an imminent spacer candidate in low-dimensional PVT architectures.