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

Abstract [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 Pb 2+ 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.