6.1
1.
2.
3.
4.
6
Basic semiconductor physics
Introduction
In this chapter we start with the discussion of some important concepts from
semiconductor physics, which are required to understand the operation of solar cells. After
giving a brief introduction into semiconductor physics in this chapter, we will discuss the
most important generation and recombination mechanisms in Chapter 7. Finally, we will
focus on the physics of semiconductor junctions in Chapter 8.
The first successful solar cell was made from crystalline silicon (c-Si), which still is
by far the most widely used PV material. Therefore we shall use c-Si as an example to
explain the concepts of semiconductor physics that are relevant to solar cell operation.
This discussion will give us a basic understanding of how solar cells based on other
semiconductor materials work.
The central semiconductor parameters that determine the design and performance of
a solar cell are:
Concentrations of doping atoms, which can be of two different types: donor
atoms, which donate free electrons or acceptor atoms, which accept electrons.
The concentrations of donor and acceptor atoms are denoted by N D and N A ,
respectively, and determine the width of the space-charge region of a junction, as
we see in Chapter 8.
The mobility µ and the diffusion coefficient D of charge carriers is used to
characterize the transport of carriers due to drift and diffusion, respectively,
which we will discuss in Section 6.5.
The lifetime τ and the diffusion length L of the excess carriers characterize the
recombinationgeneration processes, discussed in Chapter 7.
The band gap energy E g , and the complex refractive index n − ik, where k is
linked to the absorption coefficient α, characterize the ability of a semiconductor
to absorb electromagnetic radiation.
1.
2.
3.
4.
6
Basic semiconductor physics
Introduction
In this chapter we start with the discussion of some important concepts from
semiconductor physics, which are required to understand the operation of solar cells. After
giving a brief introduction into semiconductor physics in this chapter, we will discuss the
most important generation and recombination mechanisms in Chapter 7. Finally, we will
focus on the physics of semiconductor junctions in Chapter 8.
The first successful solar cell was made from crystalline silicon (c-Si), which still is
by far the most widely used PV material. Therefore we shall use c-Si as an example to
explain the concepts of semiconductor physics that are relevant to solar cell operation.
This discussion will give us a basic understanding of how solar cells based on other
semiconductor materials work.
The central semiconductor parameters that determine the design and performance of
a solar cell are:
Concentrations of doping atoms, which can be of two different types: donor
atoms, which donate free electrons or acceptor atoms, which accept electrons.
The concentrations of donor and acceptor atoms are denoted by N D and N A ,
respectively, and determine the width of the space-charge region of a junction, as
we see in Chapter 8.
The mobility µ and the diffusion coefficient D of charge carriers is used to
characterize the transport of carriers due to drift and diffusion, respectively,
which we will discuss in Section 6.5.
The lifetime τ and the diffusion length L of the excess carriers characterize the
recombinationgeneration processes, discussed in Chapter 7.
The band gap energy E g , and the complex refractive index n − ik, where k is
linked to the absorption coefficient α, characterize the ability of a semiconductor
to absorb electromagnetic radiation.