Symmetrical Acceptor–Donor–Acceptor Molecule as a Versatile Defect Passivation Agent toward Efficient FA 0.85 MA 0.15 PbI 3 Perovskite Solar Cells

Despite the swift development in perovskite solar cells (PSCs), suppressing the ion defects in the perovskite bulk and further extending the long-lasting stability of the cells remain the concerned issues that are yet to be solved. Here, a symmetrical organic acceptor−donor−acceptor (A−D−A) molecule with the core architecture of indaceno[1,2-b:5,6-b']dithiophene (IDT) and bilateral arms of oxindole, named IDT-OD, as a versatile defect passivation agent, is adopted to inactivate the nonradiative recombination sites in the perovskite absorber. The S element in the IDT unit and carbonyl group CO in the bilateral acceptor unit as the Lewis-base contributes to the passivation sites that are the under-coordinated Pb2+ cation defects and the N−H group in oxindole unit interacts with halide dangling bonds. The molecular structure with its symmetrical double arms assists the formation of a superior perovskite layer with enlarged grain size, smooth surface topography, hydrophobic property, and low density of defect state. Consequently, the corresponding PSCs with the proper IDT-OD additive yield a remarkable increase in efficiency from 22.77% to 24.04%, along with excellent long-term environmental and thermal stabilities. This study offers a propitious approach for ionic defect passivation engineering toward high-performance PSCs.