Metal halide perovskite has emerged as a next-generation candidate for the active layer of photodiodes by replacing silicon due to its excellent optoelectronic properties such as high absorption coefficient, long carrier lifetime and light absorption selectivity. Perovskite can absorb light selectively because their band gap can be tuned by changing the composition of halide at the X site. However, it is still challenging to synthesize metal halide perovskites absorbing blue light.
It is well known that the ratio of chlorine (Cl) in X site should be increased to absorb light in the short wavelength (400 nm ~ 520 nm) region and lead acetate (Pb(CH₃COO)₂) has been widely used in the synthesis process because of its low solubility of Cl. However, lead acetate accelerates the nucleation of perovskite and reduces the grain size, which makes it difficult to improve perovskite photodiodes (PePDs) performance. To enlarge the grain size of the perovskite, some methods, such as solvent engineering, interface engineering, and incorporating additives into the perovskite film have been reported. In this study, we inserted the Pb(SCN)₂ layer into the interface between ITO and perovskite to increase the grain size of the perovskite, and we report its effects on the properties of PePDs as a function of the thickness of the Pb(SCN)₂ layer.