Stanford University researchers have just announced that they have developed a new type of ultra-thin solar cell, and that it could absorb up to 10 times the amount of sunlight that current solar cells absorb. The new cells consist of several layers of organic polymer – each layer is actually thinner than the wavelength of light. By stacking each of these ultra thin layers on top of each other, and configuring each of the layers, the new cell stops light from bouncing around like it normally would in a conventional solar cell, which allows it to be more easily absorbed – a technique called “light trapping.”
“The longer a photon of light is in the solar cell, the better chance the photon can get absorbed,” said Shanhui Fan, associate professor of electrical engineering at Stanford. While light trapping has been used with some success in current silicon solar cells by roughening the surface of the cell so that light doesn’t reflect back out, it really hasn’t lead to that much of an efficiency increase in silicon based solar cells. But since the Stanford researchers are working on a nanoscale level, they found that the amount of light absorbed due to this light trapping technique increases tremendously. The team worked through multiple simulations of different light trapping permutations, and came up with a cell that consists of a multiple organic thin film layers sandwiched between two “cladding” layers that serve to keep the light inside the cell once it gets there.