The earth receives a huge amount of sunlight every hour. Converted to electricity, this would amount to 52 PW/hr. This is more than ten times the entire amount of electricity produced per hour by China in 2013. In the same year, top countries of the world together produced only 16 PW/hr. of electricity. As this is much less than the actual potential of generation of electricity from the solar energy falling on the planet earth, several countries are actively engaged on research and development on photovoltaic cells.
There have been several breakthroughs in photovoltaic cell technology. For instance, early cells were very expensive and inefficient—almost $1800/watt and 4% respectively. Costs have now come down to $0.75/watt, while the efficiency has increased to 40%. Since, then, there have been several other breakthroughs in the solar cell domain.
Printable Solar Cells
At the New Jersey Institute of Technology (NJIT), researchers have developed a printable solar cell, and they can print or paint this on a surface. According to the lead researcher Dr. Mitra, they are aiming for printable sheets of solar cells that any home-based inkjet printer will be able to print and place on the wall, roof, or billboard to generate power. The printable cells are made of carbon nanotubes 50,000 times smaller than a human hair.
All-Carbon Flexible Solar Cells
Scientists at the Stanford University have made these flexible solar cells from a special form of carbon called graphene. According to Zhenan Bao, one of the team and a professor of chemical engineering at Stanford, the flexible carbon solar cells can be coated on to the surface of cars, windows, or buildings for generating electricity.
By replacing expensive materials when manufacturing conventional solar cells, the all-carbon solar cell is expected to make the cells much cheaper.
Transparent Solar Cells
At the Michigan State University, a team of researchers has made solar cells that appear transparent to the visible spectrum of sunlight. Rather, these non-intrusive solar cells convert light beyond the visible spectrum to electricity. Therefore, these can be used on smartphones, on windowpanes of buildings, or in windshields of vehicles without impeding their performance.
According to MSU assistant professor Richard Lunt, their aim is to produce solar harvesting surfaces that are invisible. However, the present efficiency of these cells is a mere 1%, as they are in their initial stages.
Wearable Ultra-Thin Solar Cells
In South Korea, at the Gwangju Institute of Science and Technology, scientists have used gallium arsenide to develop solar cells with a thickness of just one micrometer, more than 100 times thinner than human hair. According to Jongho Lee, an engineer at the institute, such thin cells can be integrated into fabric or glass frames to power the next wave of wearable electronics.
To create such thin cells, the scientists removed extra adhesives from the traditional cells, and cold-welded them on flexible substrates at 170°C.
Solar Cells with 100% Efficiency
By extracting all the energy from excitons, researchers at the University of Cambridge have found methods of making solar cells that are more efficient. Such a hybrid cell combines organic material and inorganic material into high conversion efficiency.