Solar energy is arguably our most viable low cost energy source. It is forever sustainable and easily captured and converted. But now the technology may have taken yet another leap forward. To date the foundational technology behind photovoltaics was a structure called perovskite, which has been made with lead. Using tin instead of lead perovskite as the harvester of light, a team of Northwestern University researchers has created a new solar cell with “good efficiency”. This good efficiency solar cell is low-cost, environmentally friendly and can be easily made using “bench” chemistry — no fancy equipment or hazardous materials.