Plasmonic properties were developed as a solution for overcoming the restricted light absorption in the thin film pv devices, and consequently different plasmonic solar cell types have been developed.
How plasmonic solar cells work?
Plasmonic light trapping by metallic elements is of specific interest for the enhancement of the thin film solar cells efficiency. The interface between a metal and a dielectric semiconductor helps support surface plasmons (the collective oscillations of the conduction electrons in metals bound to the light oscillations in both dielectric and metal). The surface plasmons can be excited in either metallic nanoparticles (localized with limited spatial extent), or along the metal dielectric interface named SPP (surface plasmon polaritons), where it propagates and confines light at the interface. Using plasmonic elements improves the solar cell efficiency by concentrating light or trapping it at the absorber layer and also serves as a back contact or a cheap anti reflective electrode as well.
Incident light at the resonance frequency of the plasmon causes electron oscillations at the nanoparticles surface. Then the oscillation electrons are captured by the conductive layer, thus producing the electrical current. The produced voltage is dependent on the potential of the electrolyte in contact with the nanoparticles and the conductive layer’s band gap.
Types and properties of plasmonic solar cells
Plasmonic enhanced solar cell is a solar cell which converts light to electrical energy with the aid of plasmons, yet the pv effect occurs in a different material.
Direct plasmonic solar cell is a solar cell which converts light into electrical energy using plasmons as the active pv material.
The thickness of plasmonic solar cells varies in the range from normal silicon cell thickness, to less than 2 μm thick. Substrates which are cheaper than silicon, like steel, glass or even plastic can be used. One of the main limitations of thin film solar cells is that they cannot absorb light as much as the thicker solar cells which are made from materials having the same absorption coefficient. This is why all methods for light trapping are really critical for thin film solar cells technology and this is why plasmonic solar cells are important.
The commercialization of plasmonic enhanced solar cells or direct plasmonic solar cells still needs extra research to enable the technology to reach the required level to go mainstream.