It's not necessary to defragment a solid state drive. Traditionally, on a spinning hard drive, when data is written to the drive it's faster if all of the sectors are in order rather than scattered all over. Spinning drives have something called "seek time", which is the amount of time it takes for the read head on the drive to move to the next sector. If the read head has to move around a lot, that seek time adds up and the drive gets slower.
Flash memory, or solid state drives, have zero seek time. They have "random access." It takes no more time to read two sectors on opposite sides of the drive than it does to read two sectors side by side. So defragmenting a solid state drive doesn't make any sense. In fact, it could be bad for it because the more data gets written to it, the faster it wears out because it has a limited amount of write times.