Nanocrystalline solar cells

Solar Cell based on nanostructure such as nanocrystalline and nanowires have attracted more attention due to their potential for improvement of solar cell properties, such as charge collection efficiency,light absorb efficiency, fabricating small scale power source, reduce material consumption to lower the cost. A nanodome solar cell was first introduced by Pro Yi Cui, department of Electrical Engineering, Stanford University. The experiment result based on these devices shows that light absorption efficiency can be increase to 94% comparing to a convensional solar cell around 65%. And the energy conversion efficiency was improved by near 25% comparing to the solar cell which is based on flat film.

Another special designed solar cell was introduced by Pro. Yi Cui, which is using the mircowire array structure. As mentioned, with this design the solar cell reduce the material comsumption to 1% of a common single crystal but without lowering the energy conversion efficiency. The potential for applications of this device is further enhanced because a clever device design leads to very efficient light absorption. Specifically, the arrays were coated with silicon nitride as an antireflection coating, followed by the deposition of optically transparent Al2O3nanoparticles. These nanoparticles scatter the incoming light towards the microwires so that light absorption is maximized. The entire microwire array functions as a highly efficient light trap in which sunlight

These structures make use of some of the same thin-film light absorbing materials but are overlain as an extremely thin absorber on a supporting matrix of conductive polymer or mesoporous metal oxide having a very high surface area to increase internal reflections (and hence increase the probability of light absorption). Using nanocrystals allows one to design architectures on the length scale of nanometers, the typical exciton diffusion length. In particular, single-nanocrystal ('channel') devices, an array of single p-n junctions between the electrodes and separated by a period of about a diffusion length, represent a new architecture for solar cells and potentially high efficiency.