Effect of 2D Capping Layer on Optical Properties of 3D Methylammonium Lead Iodide Perovskites

Hybrid Organic-Inorganic Perovskites, HOIPs, have been studied extensively and grown in popularity. Three-dimensional (3D) CH
₃
NH
₃
PbI
₃
perovskites have achieved power conversion efficiency (PCE) over 23% by 2019. Nevertheless, pinholes in the perovskite film induce a huge leakage current which can cut down device efficiency by creating a short circuit. Therefore, it is essential to deposit a compact film with passivated defects. Two-dimensional (2D) halide perovskites, conversely attracted significant attention and become a positive alternative with their uncomplicated synthesis, stability and excellent photoelectric properties. This study, investigates the formation and properties of 2D tetrabutylammonium lead halide (TBAPbBr
_x
I
_3-x
) HOIP. The 2D perovskite structure was confirmed by the XRD spectrum and SEM images. The 2D nature of the compound establishing and favours highly oriented crystals with only a few grain boundaries. However, the absorption spectrum of the film shows an excitonic peak at 411 nm and a clear band edge at 450 nm. The poor light absorbance in the visible range limits the ability of TBAPbBr
_x
I
_3-x
use alone in the solar cells. However, TBAPbBr
_x
I
_3-x
can use as a separate layer on the top of the 3D perovskite layer as a capping layer to close the pinholes in the 3D perovskite layer. The incorporation of TBAPbBr
_x
I
_3-x
onto CH
₃
NH
₃
PbI
₃
shows better film formation. The application of 2D perovskite capping layer will result in better structural and optoelectronic properties.