Micromolecule Postdeposition Process for Highly Efficient Inverted Perovskite Solar Cells

Inverted perovskite solar cells (PSCs) have achieved great development, contributed by the advance of self-assembled monolayer (SAM) hole-transporting layers (HTLs) due to their distinctive molecular designability. However, SAM HTLs still present challenges of achieving a compact and ordered surface, resulting in vacancies and defects at the interface as well as adversely affecting the growth of perovskites. In this work, we propose a micromolecule postdeposition process to design the SAM HTL interface and form high-quality perovskites to achieve highly efficient inverted PSCs. We introduce etidronic acid (EA) as a postdeposition micromolecule to fill and reduce vacancies at the SAM interface and to improve growing high-quality perovskites. The postdeposition EA can anchor to the substrate through P-OH anchors, occupying vacancies left by MeO-4PACz, and simultaneously create interaction with perovskites by P=O and C-OH functional groups. The micromolecule postdeposition process effectively fills and reduces vacancies at the SAM interface, passivates defects of perovskites, and facilitates carrier transport. Consequently, a champion PCE of 24.42% is achieved for the target PSCs, which is much higher than the efficiency (20.08%) of the control. This research provides a guided and widely applicable strategy for the development of the SAM interface and further advances the performance of PSCs.