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Traps and structural defects at the hole and electron transport interfaces of the microcrystalline absorber limits the efficiency and long-term stability of perovskite solar cells (PSCs) due to accumulation of the ionic clusters, non-radiative recombination and electrochemical corrosion. Surface engineering using self-assembled monolayers (SAM) was considered as an effective strategy for modification of charge-collection junctions. In this work, we demonstrate the first report about complex integration of a SAM for double-side passivation in p-i-n PSCs. Integrating the novel 5-(4-[bis(4-fluorophenyl)amino]phenyl)thiophene-2-carboxylic acid (FTPATC) as a fluorinated SAM at the hole-transport interface reduced potential barriers and lattice stresses in the absorber. At the electron-transport side, FTPATC interacted with the A-site cations of the perovskite molecule (Cs, formamidinium), inducing a dipole for defect compensation. Using the passivation approach with fluorinated SAM demonstrated benefits in the gain of the output performance up to 22.2 %. The key-advantage of double-side passivation was confirmed by the enhanced stability under continuous light-soaking (1-sun equivalent, 65 °C, ISOS-L-2), maintaining 88 % of the initial performance over 1680 h and thermal stabilization under harsh heating at 90 °C.

To achieve commercial viability, organic solar cells (OSCs) must balance efficiency, stability, and cost. Currently, the most efficient OSCs are still based on fused ring electron acceptors (FREAs). However, their synthesis is complex, laborious, and requires numerous purification steps, which hinders the scaling and commercialization of OSCs based on them. Non–fused ring electron acceptors (NFREAs) offer the advantage of flexible chemical modulation, which significantly reduces synthetic complexity. Currently, the power conversion efficiency (PCE) of NFREA-based OSCs is approaching record highs, already exceeding 17%. However, to develop efficient and affordable OSCs, a clear understanding of the molecular design principles of successful NFREAs is critical. This review focuses on the comparative analysis of the best small molecule symmetric and asymmetric NFREAs with different molecular designs that showed PCEs above 14% and 12%, respectively. In addition, novel high–performance polymer NFREAs are analyzed. Furthermore, we discuss efficient strategies to achieve planar and rigid molecular structures of NFREAs, analyze their stability and calculate the synthetic complexity and the figure–of–merit (FoM) values for the most promising NFREAs compared to well-known FREAs. Finally, we evaluate the relationships between the structure, properties, and performance of NFREAs, and consider their prospects.