What is surface recombination velocity?

The surface-recombination velocity S is defined as the number of carriers recombining on the surface per unit area per unit time per unit volume of excess bulk carriers at the boundary between the quasi-neutral and space-charge regions [12].

Which factors affect the surface recombination?

Factors affecting Recombination

• Number of minority carriers at the edge of the junction.
• The speed with which the carriers move away from the junction.
• The speed of recombination.

How can surface recombination be reduced?

To achieve optimal operation, surface recombination is reduced by a passivating or window layer that prevents minority carriers from reaching the surface. Passivation of silicon surface by an oxide layer or the deposition of a thin “window” layer of GaAlAs on GaAs solar cells are just two examples of such practice.

What is surface recombination in solar cells?

A BSF increases the voltage of a solar cell. An extra heavy doping at the rear establishes a field that keeps minority carriers (in this case, electrons) from the highly recombining rear surface. The reduction in recombination increases the electron concentration in the base and so the solar cell’s voltage.

What is Auger recombination?

Auger recombination is a non-radiative process involving three carriers. Direct Auger recombination occurs when an electron and hole recombine, but instead of producing light, either an electron is raised higher into the conduction band or a hole is pushed deeper into the valence band, as shown in Fig.

What is recombination losses in solar cells?

Recombination losses effect both the current collection (and therefore the short-circuit current) as well as the forward bias injection current (and therefore the open-circuit voltage). Recombination and collection in a solar cell. The animation proceeds automatically.

How can you reduce surface recombination in solar cells?

To prevent rear surface recombination in a solar cell, we can create a more heavily P-Doped region near the back edge of the cell to remove latent electrons in the structure. This more heavily P-Doped region, or P+ region, is called the Back Surface Field, or BSF.

What causes Auger recombination?

Auger recombination is a non-radiative process involving three carriers. Direct Auger recombination occurs when an electron and hole recombine, but instead of producing light, either an electron is raised higher into the conduction band or a hole is pushed deeper into the valence band, as shown in Fig. 9.5(a).

What is recombination in pn junction?

This term is used frequently to describe the mechanism of current flow in a forward biased PN junction. It is called “recombination current”, where recombination is the process of conduction electrons filling holes in the valence band, thus eliminating an electron-hole pair.

What are recombination losses?

Recombination losses effect both the current collection (and therefore the short-circuit current) as well as the forward bias injection current (and therefore the open-circuit voltage). Recombination is frequently classified according to the region of the cell in which it occurs.

What is the effect of recombination time on quantum efficiency?

While quantum efficiency ideally has the square shape shown above, the quantum efficiency for most solar cells is reduced due to recombination effects. The same mechanisms which affect the collection probability also affect the quantum efficiency.