Conventional transparent and flexible solar cells are often based on the use of expensive silicon and indium tin oxide as the electrodes. While these solar cells have shown the promise of high energy efficiency, their high cost is the major setback for global adoption. Researchers at MIT have now produced a new kind of photovoltaic cell that utilized flexible graphene coated with a layer of nanowires. The new approach could be used to create transparent and flexible photovoltaic cells that could be installed on windows, roof and other surfaces.
The problem with silicon based solar cells is their high cost because silicon has been be highly purified and then converted into crystals that can be sliced thin. Moreover the use of indium tin oxide (ITO) as electrodes only increases the cost. Unlike the conventional, researchers at MIT have produced similar results using graphene that is made using ubiquitous carbon.
In addition to reducing the cost of solar cells, the new material also is flexible, light in weight and chemically robust. The research team used a series of polymer coatings on graphene to modify its properties allowing it to bond with a layer of zinc oxide nanowires and then overlay either lead-sulfide quantum dots so that it can respond to light waves.
The team has demonstrated that the devices made using graphene have a comparable efficiency to ITO, with an overall power conversion efficiency of 4.2 percent. Moreover, the manufacturing process doesn’t require high-temperature growth and instead a solution-based process can be completed below 175 degrees Celsius. While the team hasn’t demonstrated the scalability of the production process, the team is highly confident that their proof-of-concept device is scalable and can easily be commercialized.