Solar panels: Great idea if you're a spaceship, not so good anywhere it gets dark. There are some ways around this limitation, but MIT had a better idea: they invented a photovoltaic panel that doesn't need sunlight at all, and they've built it into a button-sized generator that can run your smartphone for a week straight.
What you're looking at in the above picture are a whole bunch of little tiny electric generators just a bit larger than your thumbnail. You put fuel (like butane) and air into one of those tubes, and they react, creating heat. What happens next is the really clever bit: the material that the generators are made out of has billions of itty bitty pits etched into it. We're talking nanoscale pits, so small that you can't possibly see them. When this pitted surface heats up, all those pits force it to emit light in several very specific wavelengths, and only those wavelengths. Then, you can put a photovoltaic cell that's also been tuned to those wavelengths right next to the material, and bam, you get electricity.
All this system is, really, is a way of converting heat into electricity. Sounds trivial, but pretty much our entire power infrastructure is based on that, and we're terrible at it. We have to do things like use heat to boil water into steam and then use the seam to spin a turbine to drive a generator to create electricity. Lots of steps, not much efficiency. MIT's photovoltaic generator is basically only one step with zero moving parts, and by constraining their material to only emit heat energy as light that the photovoltaic cell can use, the efficiency goes way up. Their prototypes use butane, but you can use anything that heats up: coal, wood, gasoline, radioactive uranium nuggets, the bottom of my laptop, erupting volcanoes, and yes, even sunlight.
Here's what you, the consumer, have to look forward to: MIT's current prototype generators are able to convert fuel into electricity with approximately three times the efficiency of a lithium-ion battery, and since they run on butane, you can just refill them and they're immediately good to go. With a bit more work, the research team at MIT is pretty sure they can triple their current level of efficiency, and since you can scale all this stuff down, MIT sees a photoelectric generator that can power your smartphone for a solid week being made a reality in the near future.