太阳能电池等效电路模型

The equivalent circuit model is a powerful tool for understanding and analyzing the electrical behavior of a solar cell. It abstracts the complex semiconductor physics into a simple circuit diagram with a few key components. The core of the model is an ideal current source that produces a current, [latex]I_L[/latex], directly proportional to the incident light intensity. This represents the generation of electron-hole pairs by photons.

In parallel with this current source is a diode. This diode models the behavior of the p-n junction itself. In the dark, the solar cell is just a diode, and its current-voltage (I-V) characteristic follows the ideal diode equation. When illuminated, some of the photogenerated current is shunted through this internal diode, a process known as recombination, which does not contribute to the output current. The total output current [latex]I[/latex] is therefore the photogenerated current minus the diode current: [latex]I = I_L – I_D[/latex].

For a more realistic representation, two parasitic resistances are added. A series resistance, [latex]R_s[/latex], accounts for the resistance of the metal contacts, the emitter, and the bulk semiconductor material. It causes a voltage drop that reduces the terminal voltage and the fill factor. A shunt resistance, [latex]R_{sh}[/latex], is placed in parallel with the diode and current source. It represents leakage paths for the current across the p-n junction, often due to manufacturing defects. A low shunt resistance provides an alternate path for the photogenerated current, reducing the current delivered to the load. The governing equation for this single-diode model is: [latex]I = I_L – I_0 \left[ \exp\left(\frac{V+IR_s}{n k_B T/q}\right) – 1 \right] – \frac{V+IR_s}{R_{sh}}[/latex], where [latex]I_0[/latex] is the diode saturation current and [latex]n[/latex] is the ideality factor.