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PN结光伏原理

1940

Russell Ohl

(generate image for illustration only)

A solar cell’s core is a p-n junction, an interface between p-type and n-type semiconductor materials. This junction creates a built-in electric field in a depletion region. When photons with sufficient energy strike the semiconductor, they create electron-hole pairs. The electric field separates these charge carriers, driving electrons to the n-side and holes to the p-side, generating a voltage.

pn结是大多数太阳能电池的基本组成部分。它由空穴（正电荷载流子）过剩的p型半导体与电子（负电荷载流子）过剩的n型半导体连接而成。这通常是通过在单个半导体晶体（例如硅）的两侧掺杂不同的杂质来实现的。

At the interface, electrons from the n-side diffuse into the p-side, and holes from the p-side diffuse into the n-side. This diffusion process doesn’t continue indefinitely. As electrons and holes cross the junction, they recombine, leaving behind ionized donor atoms on the n-side and ionized acceptor atoms on the p-side. This creates a region depleted of free charge carriers, known as the depletion region or space charge region. The fixed, ionized atoms in this region establish a strong, static electric field pointing from the n-side to the p-side.

This built-in electric field is crucial for the photovoltaic effect. When a photon with energy greater than the semiconductor’s bandgap energy ([latex]E_g[/latex]) is absorbed, it excites an electron from the valence band to the conduction band, creating an electron-hole pair. If this pair is generated within the depletion region or close enough to diffuse into it, the electric field acts on them. The field sweeps the electron towards the n-side and the hole towards the p-side. This separation of charge prevents immediate recombination and creates an accumulation of positive charge on the p-side and negative charge on the n-side. This charge separation across the device results in a photovoltage, which can drive a current through an external circuit, thus converting light energy into electrical energy.