Fully Conjugated Co-Self-Assembled Monolayers for Efficient and Stable Inverted Perovskite Solar Cells

[4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) consistently exhibits inhomogeneous distribution on the substrate, which makes it a challenge for the growth of high-quality perovskite film, resulting in undesired interfacial losses at buried interfaces. Moreover, the flexible alkyl chains of Me-4PACz are not conducive to intermolecular interactions and hinder charge flow. Here, a novel molecule with 4-Methoxy-N-(4-methoxyphenyl)-N-phenylaniline (TPA) and carbazole backbone, named CzTPA is designed, which constituted Co-SAM with Me-4PACz. The two carboxyls on the end of carbazole will act as an anchoring group to cover the inadequate coverage of Me-4PACz on the NiO_x. The methoxy group on the TPA can passivation the uncoordinated Pb²⁺ at the perovskite buried interface by the interaction of Pb─O. Additionally, the Me-4PACz can be restrained self-aggregation by interacting with the TPA group of CzTPA. The cooperation of CzTPA realizes the more homogeneous distribution of Me-4PACz on the NiO_x, efficient charge transport, and minimize buried interfacial defects. Accordingly, the CzTPA modification can significantly enhance the efficiency of 1.54-eV PSCs from 23.53% to 25.66% and sustain 91.4% of its original efficiency after 1992 h under continuous illumination at 65 °C. More importantly, a 1.68 eV of wide-bandgap PSC achieved a PCE of 22.75% with good photostability.