A recent article in Phys.org talks up the ever increasing stability of perovskites, yet still their main problem is that they deteriorate in the sun. And doing well in the sun is the most important thing for a solar panel.
Solar panelsthat are installed at an angle (in line with a pitched roof or on tilt frames) are generally self cleaning. However in dry, dusty areas or where panels are installed flat; dirt dust, grime and other substances such as bird droppings can build-up reducing the power output of the PV panels. Due to the nature of solar panels grime and bird droppings doesn’t need to cover an entire panel to reduce output significantly.