Solar cells have evolved significantly since 1883 when thin, gold-coated selenium achieved an energy conversion rate of 1-2%. Through a series of advancements, today’s silicon-based solar cells can convert light to electricity by 15–20%. However, it was not until the early 1950s that silicon solar cells were commercially available for photovoltaic (PV) technology. Mere commercial availability did not make a positive market impact due to the high-costs associated with the technology. The first major application for the solar cell came in the form of space exploration, as the technology gained support from the US government. The technology evolved significantly due to consistent research funding by major companies and a sustained interest to replace oil as a fuel. The efforts resulted in increased cell efficiency and lowered the cost-per-watt. In the 1990’s, solar cells reached a new landmark of producing 30% conversion efficiency––achieved with the help of gallium-based materials. Towards 2000, the National Renewable Energy Laboratory created thin-film solar cells or second-generation solar cells. After consistent research efforts, the industry successfully demonstrated manufacturable flexible solar cells in 2015. Although the technology is still in the research phase, it is inevitable to understand the various benefits that the technology can produce.
Flexible solar cells are made possible through the flexible substrate and the ability to process coatings over it. Printed flexible solar cells are produced in the form of strips and can achieve a conversion efficiency that is slightly lower than that of conventional solar cells. Furthermore, technology can produce up to 50 watts per square meter and is cheaper.
Recent developments in solar cell technology have followed the traditional steps of evolution. The combination of new materials and processes in terms of developing solar cells has worked well for a team of MIT researchers. The development of flexible solar cells was not only enabled by flexible graphene electrodes, but also by MIT researchers, who developed a novel processing method to characterize the material to the requirement. On a general note, organic flexible solar cells are said to provide various benefits over traditional silicon-based, rigid solar cells. Transparent and organic solar cells are also easier and cheaper to manufacture, making them more affordable. Furthermore, the light weight and flexibility of organic solar cells enable them to widen the application where conventional solar cells have limits. For example, due to these solar cells being lightweight, it could be transported and installed with ease in structure-sensitive applications such as roofs and walls. Moreover, this flexibility will leverage the capability of these solar cells to be mounted on any surface without limitation. Therefore, the transparency and flexibility of the solar cell could find application in laptops, smartphones, car roofs, and so forth.
Solar cells based on flexible graphene electrodes faced several challenges in processing and characterization before this technology was fully integrated as a cell. Cells thus created are expected to be novel innovations in the market, as they are poised to be cheaper than ever. Most of all, the graphene is one of the most abundant and ubiquitous forms of carbon; also, the material is flexible, transparent, durable, and highly conductive, which proves to be a worthy investment to exploit further. For instance, the optical transmittance of graphene-based solar cells is estimated to be over 60%, making it the highest among all transparent solar cells. It is also believed that such solar cells could be grown directly on any surface, rather than manufacturing it discretely and then assembling it.
Therefore, the graphene-based flexible solar cell is deemed to be a breakthrough innovation in the field of solar energy. However, researchers in this sector are said to be continuing to focus on improving the power conversion efficiency to make it more commercially viable.
In summary, flexible solar cells have progressed significantly over the last decade through the advancements in material characterization and processing techniques. The latest advancements in the industry throw a promising light towards cheaper solar cells being available for the commercial market. The flexibility, transparency, and durability of organic flexible solar cells widely expand the boundaries of applicable solar energy. However, although current advancements do not convert light to electricity as efficiently as conventional solar cells, it is certain that flexible solar cells will find renewed interest among funding agencies, and eventually become a viable commercial product sooner than expected.
