In
perovskite solar cells, the halide vacancy defects on the perovskite
film surface/interface will instigate charge recombination, leading
to a decrease in cell performance. In this study, cadmium sulfide
(CdS) has been introduced into the precursor solution to reduce the
halide vacancy defects and improve the cell performance. The highest
efficiency of the device reaches 21.62%. Density functional theory
calculation reveals that the incorporated Cd2+ ions can
partially replace Pb2+ ions, thus forming a strong Cd–I
bond and effectively reducing iodide vacancy defects (VI); at the same time, the loss of the charge recombination is significantly
reduced because VI is filled by S2– ions.
Besides, the substitution of Cd2+ for Pb2+ could
increase the generation of PbI2, which can further passivate
the grain boundary. Therefore, the stability of the cells, together
with the efficiency of the power conversion efficiencies (PCEs), is
also improved, maintaining 87.5% of its initial PCEs after being irradiated
over 410 h. This work provides a very effective strategy to passivate
the surface/interface defects of perovskite films for more efficient
and stable optoelectronic devices.