definitely wash before freezing. Kinda hard to wash a previously frozen, now thawed, mushy pod. Whether to freeze whole or half is up to you.
Side note for drying frozen pods... The frozen chiles will release a TON of liquid when they thaw out and can cause problems with all the liquid draining down onto the dryer unit. Either defrost in a colander to let the bulk of the liquid drain away before puting into the dehydrator, or, if you have those plastic trays for making fruit leather for the dehydrator, put that on the lowest tray to catch the juice from the frozen pods.