At present, most of the commercially available single-sided solar cells can convert sunlight to energy at an average efficiency of around 21%. This is very low. For comparison, internal combustion engines converts fossil fuel to power at an efficiencies above 35%. Thus, there is a lot more potential when it comes to solar cell energy conversion. Bifacial panels can provide efficiencies upto 40%. However, they are just two-sided solar panels which also converts, the otherwise lost, diffused and scattered solar irradiation in the visible spectrum. Theoretically, single junction cells has a limit between 29 and 3%, called the Shockley-Queisser limit.
New research hints at the possibility of transforming low energy light (invisible light) to high energy photons that can be captured by solar cells. This process converts light that is less energetic than the near Infrared through a photochemical upconversion with oxygen. RMIT University, UNSW University and the university of Kentucky (USA) lead this study.
Another approach in the research of high efficiency solar cells comes from the Okinawa Institute of Technology. Instead of silicon, a type of material called perovskites are employed. Such cells are economic and light weight. In general, the main bottlenecks of perovskites-based solar cells include scalability and life span. Any defects in materials gets amplified during the scale-up and results in poor efficiency as compared to silicon-based cells. Furthermore, perovskites-based cells degrade faster resulting in a smaller life span. The Okinawa research team used a multi-layer perovskites set-up. This performed at efficiency of 16.6% (for a size of 22.4 sq. cm) for an time of 2000 hours operational time.