Semiconducting Covalent Organic Frameworks as Functional Dopants for Efficient Perovskite Solar Cells

This study presents the first comprehensive investigation of pyrene-based covalent organic frameworks (COFs) as bulk dopants in formamidinium lead iodide (FAPbI₃) perovskite solar cells (PSCs). A series of three frameworks-sp²c-PyCOF, Im-PyCOF, and SH-PyCOF-were synthesized to systematically evaluate the effects of distinct linkage chemistries and Lewis-basic functionalities (-C≡N, -C = N-, and -SH) on perovskite optoelectronic performance. When incorporated into the perovskite precursor solution, the PyCOFs coordinate with undercoordinated Pb^{2 +} sites, effectively passivating deep trap states and suppressing non-radiative recombination. Their extended π-conjugation further promotes efficient charge delocalization and transfer within the bulk perovskite. Consequently, PyCOF-doped PSCs demonstrated enhanced charge extraction and higher Fill Factors, achieving champion power conversion efficiencies of ∼19.5%, outperforming both undoped devices (17.75%) and pyrene-free COF controls. These findings establish π-conjugated pyrene COFs as a new class of multifunctional dopants that couple structural stability with optoelectronic tunability, offering a rational molecular design platform for the next-generation of high-performance and durable perovskite photovoltaics.