Series Resistance

Source: makeabilitylab.github.io
**Understanding Series Resistance in Solar Cells**

Series resistance in a solar cell can be attributed to three main factors: current flow through the emitter and base of the solar cell, contact resistance between the metal contact and silicon, and resistance of the top and rear metal contacts. The primary consequence of series resistance is a reduction in the fill factor, although excessively high values can also diminish the short-circuit current.

**Mathematical Representation**

The impact of series resistance can be mathematically expressed using the equation:

I = I L − I 0 exp [ q ( V + I R S ) n k T ]

where various parameters such as cell output current (I), light generated current (I L), voltage across the cell terminals (V), temperature (T), constants (q and k), ideality factor (n), and cell series resistance (R S) are involved. This equation represents an implicit function and necessitates numerical methods for solution.

**Effects on IV Curve**

The effect of series resistance on the IV curve of a solar cell is significant. While it does not influence the solar cell at open-circuit voltage, it notably affects the IV curve near this point. A common approach to estimating series resistance from a solar cell is by determining the slope of the IV curve at the open-circuit voltage.

**Fill Factor and Output Power**

An equation describing the fill factor as a function of series resistance can be derived by considering the power loss in the series resistance. This leads to an approximation of the effect of series resistance on the output power of a solar cell. The impact of series resistance on the fill factor can be evaluated by assuming that the open-circuit voltage and short-circuit current remain unaffected.

**Empirical Equations**

Empirical equations can provide a more accurate representation of the relationship between the fill factor without series resistance and with series resistance. These equations are particularly valid for specific ranges of series resistance and open-circuit voltage.

**Conclusion**

Series resistance plays a crucial role in the performance of solar cells, affecting parameters such as fill factor and output power. Understanding the impact of series resistance is essential for optimizing the efficiency of solar cell systems.

Source: Teachoo

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