I don’t know if this is the world’s only solar light bulb, but the Nokero Solar Light Bulb certainly looks useful for off-grid situations. It charges its AA-sized NiMH batteries with a high-efficiency solar panel, and it can provide 6+ hours of 13.5 lumens of light from its four LEDs. The bulb has a shatter-resistant polycarbonate globe, and it’s rain resistant. After charging, it works great in your tent or in your home in lieu of candles during a power outage. It’s also small and light enough to store in your emergency preparedness kit. You get a set of three Nokero Solar Light Bulbs for $49.99 from Amazon.