Of course they work best in direct sunlight. But they're also efficient in cloudy weather. It's not just good news, it's wonderful news when you consider it was an embryonic technology less than twenty years ago. It's come on leaps and bounds. As evidenced by the picture posted a few pages back, oftentimes its output will be ~40-50%. Even with output ~5%, it's still a worthy energy source; to put that into perspective, that 5% figure would be enough to power the whole of Greater Manchester. All renewable energy sources, in the here and now, should be used supplementarily. Fossil fuels are still needed, but the need to transition to renewable is far more pressing.
Some think that advocates of renewable are all tree huggers who eat tofu and walk around barefoot; but it's not just a case of cutting carbon emissions and being kinder to the planet: the reality is this, one day fossil fuels will run out. Poof, they will be gone. Conservative estimates put that fateful expiry date about sixty years from now, and if we haven't harnessed the full potential of renewable by that point, then you can kiss goodbye to your great-grandchildren leading any kind of normal life.
Thankfully, people much smarter than I or anyone on this forum are working tirelessly to avert such a catastrophe.