Rational Design of Rhodanine‐Based Hole‐Selective Layers for Optimizing Interfacial Passivation in High‐Performance Wide‐Bandgap Perovskite Solar Cells

Abstract

ABSTRACT Wide‐bandgap (WBG) perovskite solar cells (PSCs) are promising candidates for indoor photovoltaics (IPVs), but their efficiency is limited by non‐radiative recombination at the buried perovskite/transport layer interface. To reduce these losses, this study proposes using self‐assembled monolayers (SAMs) combining a triphenylamine (TPA) donor with rhodanine (RH) or rhodanine‐3‐acetic acid (RA) anchoring groups, as effective hole‐selective layers (HSLs). Using NiOx/SAM double HSLs, we found that the heteroatom‐rich RA group with a carboxymethyl co‐anchor enhances NiOx surface oxidation and provides strong interfacial passivation. DFT calculations, electrochemical analysis, and characterization via XPS, UPS, PL, and SEM were used to elucidate the HSL–perovskite interface relationship. Structural studies revealed that the molecular spacer influences perovskite growth. Sterically hindered TPA‐AN‐RA yields smaller grains with more defects, while planar TPA‐PH‐RA enables larger grains and fewer traps. The optimized TPA‐RA structure ensures balanced energetics and improved charge extraction, delivering an impressive indoor iPCE of 41.81% under a 1000 lux white LED. Under AM 1.5G conditions, it achieves 18.68% PCE, making it suitable for hybrid lighting environments. Furthermore, the unencapsulated TPA‐RA device retained 84% of its indoor efficiency after 1600 h in an inert atmosphere, demonstrating excellent intrinsic stability. This work highlights the potential of molecular engineering for producing high‐efficiency stable indoor PSCs.