**3.3 Additive treatment**

An additive is a substance added to something in small quantities to improve it in some way. It is another parameter affecting the morphology of perovskite. Additives can be added in two ways: one is to add additives in perovskite precursor and the other is to add them in the antisolvent. In additive treatment, the following considerations must be optimized;

First and foremost, additives must be soluble in perovskite dissolvents. If not, they should be added into the antisolvent [24]. The basic roles of additives are as follows:


Various anti-solvents were reported in literature, such as hydroiodic acid (HI), sulfobetaine zwitterion, Chlorine ion additives, ionic liquid (methyl formate), dimethyl sulfoxide (DMSO), etc.

#### *Optimal Conditions for Preparation of Perovskite Materials for Optoelectronic Devices DOI: http://dx.doi.org/10.5772/intechopen.107992*

For instance, the aim of adding additives like HI and sulfobetaine is to stabilize the crystal structure [24], enhance the film uniformity and addressing the issue of too fast crystallization. Also, Terephthalic acid (TPA) [6, 24] and conjugated polymer [6, 24] and the likes are employed to regulate the nucleation and crystal growth of perovskite, increase the crystallinity and stability of perovskite, and minimize the defects in the film. In short, it was observed that the primary role of the additives is to passivate the grain boundaries (GBs) and prevent non-radiative recombination [24].
