Researchers in California report they\'ve built the first all-carbon solar cell, a promising alternative to today\'s photovoltaic devices that use expensive materials. Scientists at Stanford University said unlike rigid silicon solar panels found on many rooftops, their thin film prototype is made of carbon materials that can be applied as a coating. \"Carbon has the potential to deliver high performance at a low cost,\" chemical engineering Professor Zhenan Bao said in a Stanford release Wednesday. \"To the best of our knowledge, this is the first demonstration of a working solar cell that has all of the components made of carbon.\" Carbon solar cells could also be cheaper to manufacture, researchers said. \"Processing silicon-based solar cells requires a lot of steps,\" graduate student Michael Vosgueritchian, a study co-lead author, said. \"But our entire device can be built using simple coating methods that don\'t require expensive tools and machines.\" The Stanford solar cell consists of a photoactive layer, which absorbs sunlight, sandwiched between two electrodes. In a typical thin film solar cell, the electrodes are made of conductive metals and indium tin oxide. \"Materials like indium are scarce and becoming more expensive as the demand for solar cells, touchscreen panels and other electronic devices grows,\" Bao said. \"Carbon, on the other hand, is low cost and Earth-abundant.\" \"Photovoltaics will definitely be a very important source of power that we will tap into in the future.We have a lot of available sunlight. We\'ve got to figure out some way to use this natural resource that is given to us.\"