π‑Conjugation-Induced\nIn Situ Nanoscale\nOrdering of Spiro-OMeTAD Boosts the Efficiency and Stability of Perovskite\nSolar Cells

Spiro-OMeTAD hole transport materials typically exhibit\nan amorphous\nstate in perovskite solar cells. However, the lack of structural ordering\nleads to weak intermolecular interaction, inferior carrier transfer,\nand poor stability in devices. Herein, we developed a π-conjugation-induced\nshort-range ordering strategy to modulate the stacking order of spiro-OMeTAD\nduring film formation. A clear molecular ordering at the nanoscale\nis observed, which enhances intermolecular π–π\nstacking in spiro-OMeTAD and enables effective carrier extraction\nand favorable energy level alignment. The nanoscale-ordered spiro-OMeTAD\nallows the achievement of perovskite solar cells with a champion efficiency\nof 25.37%, surpassing devices utilizing amorphous spiro-OMeTAD (23.52%).\nThe unencapsulated device demonstrates enhanced operational stability\nby retaining 98% of its initial efficiency under continuous 1 sun\nequivalent illumination at 60 °C for 840 h. This work establishes\na significant and valid modulation concept for the stacking order\nof organic transport materials, paving the way for the development\nof efficient and stable perovskite solar cells.