Your system should be completely shut down before cleaning as per the shutdown procedure listed in your user manual or your inverter manufacturer's operating manual and the sticker or label affixed to the inverter.
It is highly advisable to have a knowledge of risks involved with working at height and wear appropriate fall arrest protection.
DC Systems will need to be completely shut down. AC Systems should be shut down via the Solar Supply Main Switch in your switch board.
Be aware that although the DC isolator isolates things downstream it will not isolate the solar panel generator units, if there is a electrical fault at the panels, turning off the isolator will not protect you.