Dear Mathu Sridharpanday,

Take a look at the data below:

What is the difference between amorphous silicon and crystalline silicon?

In crystalline silicon (c-Si) this tetrahedral structure continues over a large range, thus forming a well-ordered crystal lattice. In amorphous silicon this long-range order is not present. Rather, the atoms form a continuous random network. ... Due to the disordered nature of the material some atoms have a dangling bond.

Is Si crystalline or amorphous?

In general, two main categories of solar cells, wafer-based and thin-film, have achieved significant progress. Crystalline silicon (c-Si) dominates the wafer-based solar cells. On the other hand, amorphous silicon (a-Si) plays a vital role in thin-film solar cells. Yet, both types of solar cells employ silicon.

What is the advantage of an amorphous silicon over the single and polycrystalline sample?

... Polycrystalline cells are less expensive to make than single-crystalline modules but are also slightly less efficient than the single-crystalline (12% -15%). Also, it has been found that amorphous silicon cells dominate in warm, sunny conditions due to their lower power-loss temperature coefficient [1] .

https://www.sciencedirect.com/topics/chemistry/amorphous-silicon

https://www.coursera.org/lecture/silicon-thin-film-solar-cells/1-comparison-between-crystalline-and-amorphous-silicon-1LfI2

There is no general answer to this. The main differences depend on your applications. For example, single crystals are preferred when the properties of the material should not vary across the substrate and are known and specified. In other cases, you want to benefit from the crystal structure, as in the case of single crystal SiO2 (quartz), which is piezoelectric, but amorphous SiO2 is not. In other cases, one may prefer a type due to optical properties, such as birefringence for some crystals or increased optical absorption (e.g. in amourphous Si but with lowered electrical transport quality).

Thank you so much professor @len leonid mizra

The answer to "Which is best" so very often is "It depends"!!! The very same qualities that are an advantage in one application will be a disadvantage in another application. See Steffen's answer.