π-Conjugation-extended dinaphthocarbazole phosphonic acid as a hole-selective layer for perovskite solar cells

In photovoltaic technology, self-assembled monolayers (SAMs) are key hole-selective layers for inverted perovskite solar cells (PSCs), regulating hole extraction, perovskite film quality and device performance. Carbazole-based SAMs like 4PACZ are widely used but suffer from limited molecular dipole and flat-structure-induced stacking, causing poor energy alignment and incomplete substrate coverage that compromise performance.

This study designed a novel polycyclic aromatic hydrocarbon-derived SAM, 4PADNC, for optimizing hole transport in inverted PSCs by replacing 4PACZ’s single carbazole with the extended π-conjugated, electron-rich dinaphtho[2,3-c:2',3'-g]carbazole. Its enhanced molecular dipole adjusts ITO work function, while the ~34.62° intramolecular dihedral angle suppresses π-π stacking, forming dense ordered layers. Consequently, 4PADNC-based PSCs achieved a 24.32% PCE, outperforming 4PACZ’s 22.89% with superior stability.

Our findings provide a valuable approach for designing novel hole-selective materials, thereby improving the efficiency and stability of inverted PSCs. The work titled “π-Conjugation-extended dinaphthocarbazole phosphonic acid as a hole-selective layer for inverted perovskite solar cells” was published on Acta Physico-Chimica Sinica (published on Sep. 24, 2025).