Grain size control of perovskite films based on -alanine self-assembled monolayers surface treatment

The grain size of the perovskite layer can be tuned by the surface treatment of Ultraviolet ozone (UVO) with beta-alanine self-assembled molecular films (SAMs) on the Nickel oxide (NiO) x substrate. The UVO treatment had been used to control the hydroxy (-OH) end-group on NiOx substrate and the condensation reaction of beta-alanine SAMs, in which the end-group of the amino group (-NH2) correlates with the nucleation of the perovskite layer. The difference of surface end-group with/without the UVO treatment on the NiOx substrate was revealed by the shift of the oxidation peak of the SAMs layer in the cyclic voltammetry and the electrochemical impedance spectroscopy. It is found that the wettability of NiOx substrate was enhanced by the SAMs treatment time due to the increment of -NH2 end-group and the UVO treatment. Larger grain size of the perovskite layer was achieved on the NiOx substrate with SAMs 15 minutes treatment. Moreover, the optical absorbance of perovskite films in the short wavelength range was enhanced by the assembling time of SAMs. This study provides a method to control the surface morphology of the perovskite active layer in its solar cell device applications.