BBC put out an article on a Brazilian man who created a plastic bottle light, aka the Moser Lamp, to be used in low-income family homes. All one needs is a bottle, water, a little bleach and sunlight. I had heard about it before but didn’t know it was a Brazilian who invented it. Pretty creative.
If you can get BBC World Service (iPlayer), listen to an interview with him (minute 35) here, though it just repeats what’s in the article.