What is the length of diffusion?
The diffusion length of a carrier type in a material can be defined as the average distance that an excited carrier will travel before recombining. The diffusion length can be defined as follows: where D is the diffusion coefficient and τ is the lifetime of the excited carrier.
What is the characteristic diffusion length?
The diffusion length is the characteristic length scale for diffusion problems. It increases as the square root of the time. For semi-infinite regions, the solution looks the same for all times if the length is scaled by the appropriate diffusion constant for that time.
What is diffusion in solar cell?
Solid state diffusion is a straight forward process and the typical method for introducing dopant atoms into semiconductors. In silicon solar cell processing starting substrates are typically uniformly doped with boron giving a p-type base. The n-type emitter layer is formed through phosphorus doping (see Doping).
What is exciton diffusion length?
The exciton diffusion length can be calculated as LD = (Dτ)1/2, where D is the diffusion constant given by D = α/(8πR) (three-dimensional diffusion model), R is the annihilation radius of singlet excitons. The annihilation radius cannot be easily measured and generally assumed to be 1 nm21,41,42,43.
Why is the diffusion length important in solar cells?
Higher diffusion lengths are indicative of materials with longer lifetimes and are, therefore, an important quality to consider with semiconductor materials.
What is diffusion length semiconductor?
Diffusion length is the average length a carrier moves between generation and recombination. Semiconductor materials that are heavily doped have greater recombination rates and consequently, have shorter diffusion lengths.
What is an exciton in physics?
exciton, the combination of an electron and a positive hole (an empty electron state in a valence band), which is free to move through a nonmetallic crystal as a unit.
What is migration length?
where M is the migration area (m2), the migration length is defined as the square root of the migration area. As can be seen, the total non-leakage probability of large reactors is primarily a function of the migration area.
What is diffusion depth?
Overview. Diffusion length is the average length a carrier moves between generation and recombination. Semiconductor materials that are heavily doped have greater recombination rates and consequently, have shorter diffusion lengths.
What is diffusion and diffusion current?
Diffusion current Density is a current in a semiconductor caused by the diffusion of charge carriers (holes and/or electrons). This is the current which is due to the transport of charges occurring because of non-uniform concentration of charged particles in a semiconductor.
What is diffusion velocity?
The diffusion velocity is a molecular phenomenon and depends upon the gaseous concentration as well as upon the pressure and temperature gradients present. The speed with which a turbulent diffusion process proceeds as evidenced by the motion of individual eddies. Lettau, H. 1951.