ABSTRACT
Photovoltaic (PV) cells convert light energy to electrical energy through the PV effect. The PV effect causes light irradiating the PV cell to stimulate electrons to higher energy levels where they are better able to escape the PV cell into an external circuit where they are subsequently collected or harvested as electrical energy. The efficiency with which light energy is converted to electrical energy is dependent on both the characteristics of the input light including irradiance (intensity) and wavelength and also on the design of the PV cell. Although PV cells consisting of a single layer of material are possible, they are rarely used in practical applications because such one-layer cells are highly inefficient. Instead, bilayer cells consisting of a junction of two materials are the most common approach to harvest light energy although even more efficient, advanced, multijunction cells are also possible. This chapter takes a look at the fundamental principles that govern PV cell operation including relevant properties of light, basic behavior of a bilayer silicon-based PV cell, and characteristic behavior of such cells. Advanced structures including concentrators and multiple-junction cells that can improve upon basic bilayer functionality are also discussed.
