Japan's push into 'deep tech' innovation

Imagine if you could put an ultra-thin, transparent solar sheet on your window to generate energy, not just from sunlight but also artificial lights from inside your room?

Seen as the most promising next-generation solar cell, this technology, called perovskite, is exactly what Japanese start-up Enecoat Technologies is trying to develop.

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Presented by Mariko Oi for BBC News