Symmetrical Acceptor-Donor-Acceptor Molecule as a Versatile Defect Passivation Agent toward Efficient FA0.85MA0.15PbI3 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(sic)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.

Automated summary

This study adopts an organic acceptor-donor-acceptor (A-D-A) molecule called IDT-OD as a defect passivation agent to improve the efficiency and stability of perovskite solar cells (PSCs). The symmetrical double arms structure of IDT-OD molecule helps to form a superior perovskite layer, resulting in enhanced performance of the cells.