How does increasing internal series resistance $ R_s $ (e.g., from degraded metal contacts) affect the I-V characteris · Electronics MDCAT Past Paper MCQ

Physics Electronics PMDC Conceptual Practice

PMDC Verified Question 298 of 494

How does increasing internal series resistance $ R_s $ (e.g., from degraded metal contacts) affect the I-V characteristic curve and performance of a solar cell?

It increases the open-circuit voltage significantly

It eliminates all internal electron-hole recombination

It reduces the Fill Factor (FF) and maximum power output without significantly altering the open-circuit voltage

It converts the solar cell into a direct AC generator

Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:

Option C: It reduces the Fill Factor (FF) and maximum power output without significantly altering the open-circuit voltage

Concept:

Series resistance $ R_s $ causes internal $ I R $ voltage drops under load current, flattening the knee of the I-V curve, reducing the Fill Factor ($ \text{FF} $), and lowering peak power output $ P_{\text{max}} $.

Formula:

$$V_{\text{terminal}} = V_{\text{junction}} - I R_s \implies \text{Fill Factor } \text{FF} \downarrow \implies P_{\text{max}} = \text{FF} \cdot V_{\text{oc}} \cdot I_{\text{sc}} \downarrow$$

Solution:

At open circuit ($ I = 0 $), no current flows through $ R_s $, so $ V_{\text{oc}} $ remains unchanged.

Under load, current flowing through $ R_s $ reduces the terminal voltage, rounding the I-V curve and lowering the Fill Factor and maximum power output.

Why other options are incorrect:

Option A: $ R_s $ does not increase $ V_{\text{oc}} $; at $ I = 0 $, $ V_{\text{oc}} $ is unchanged.
Option B: Series resistance increases resistive losses and does not stop recombination.
Option D: Solar cells generate DC power, not AC.

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