Jan 4 2002
本文于2019年2月12日更新。
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The "photovoltaic effect" is a process through which a photovoltaic (PV) cell converts sunlight into electricity. Sunlight is composed of photons or particles of solar energy. Photons contain different energies corresponding to different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed. The absorbed photons generate electricity: the energy of the photon is transferred to an electron in an atom of the cell (which is actually a semiconductor). With its newfound energy, the electron is able to escape from its normal position within the atom to become part of the current in an electrical circuit. By leaving this position, the electron causes a "hole" to form. Special electrical properties of the PV cell provide the voltage needed to drive the current through an external load (such as a light bulb).
P型，N型和电场
为了诱导光伏电池内的电场，将两个单独的半导体夹在一起。半导体的“ P”和“ N”类型对应于“正”（孔）和“负”（电子）。
当将P型和N型半导体夹在一起时，N型材料中的过量电子流到P型中，因此在此过程中流向N型P型中的孔空隙。两个半导体充当电池，在它们遇到的地面形成电场（称为“连接”）。正是这一领域使电子从半导体跳到表面并使它们用于电路。同时，孔沿相反方向移动到正面的正面，在那里它们正在等待传入的电子。
制作N和P材料
Crystalline silicon was the semiconductor material used in the earliest successful PV devices. The most common way of making p-type or n-type silicon material is to add an element that has an extra electron or is lacking an electron by a process called "doping." It introduces an atom of another element into the silicon crystal to alter its electrical properties. The dopant has either three or five valence electrons, as opposed to silicon's four.
The Silicon Molecule
大量的硅原子通过其价电子可以键合形成晶体。在结晶固体中，每个硅原子通常与四个相邻硅原子中的每一个共价键共享其四个价电子之一。因此，固体硅晶体由五个硅原子的一系列常规单元组成。这种规则的固定硅原子排列称为“晶格”。
硅原子描述
The protons and neutrons in an atom are approximately equal in size and comprise the close-packed central "nucleus" of the atom, where almost all of the mass of the atom is located. The much lighter electrons orbit the nucleus at very high velocities. Although the atom is built from oppositely charged particles, its overall charge is neutral because it contains an equal number of positive protons and negative electrons. The electrons orbit the nucleus at different distances, depending on their energy level; an electron with less energy orbits close to the nucleus, whereas one of greater energy orbits farther away. The electrons farthest from the nucleus interact with those of neighboring atoms to determine the way solid structures are formed.
硅原子具有14个电子，但是它们的天然轨道排列仅允许外四个电子中的键合中的四个电子。这些称为“价”电子的外部四个电子在光伏效应中起着重要作用。
介绍硼
具有三个价电子的硼用于掺杂形成P型硅。在硅加工过程中引入了硼，其中硅被纯化用于PV设备。当硼原子在以前由硅原子占据的晶格中假设位置时，却缺少一个键，换句话说，引入了一个孔。
引入磷
Phosphorus atoms, which have five valence electrons, are used for doping to form n-type silicon. A phosphorus atom occupies the same place in the crystal lattice that was occupied formerly by the silicon atom it replaced. Four of its valence electrons take over the bonding responsibilities of the four silicon valence electrons that they replaced. But the fifth valence electron remains free. When numerous phosphorus atoms are substituted for silicon in a crystal, many free electrons become available.
吸收和传导
在PV细胞中，光子被P层吸收。将此层“调整”到传入光子的性质中，以吸收尽可能多的电子，从而自由到尽可能多的电子非常重要。另一个挑战是，在它们可以逃脱电池之前，请防止电子与孔“重新组合”。为此，我们设计了材料，以便将电子释放到尽可能靠近连接处，以便电场可以帮助它们通过“传导”层（n层）并进入电路。通过最大化所有这些特征，我们提高了PV细胞的转化效率。
Sources and Further Reading