How do the open-circuit voltage ($ V_{\text{oc}} $) and short-circuit current ($ I_{\text{sc}} $) of a photovoltaic · Electronics MDCAT Past Paper MCQ

Physics Electronics PMDC Conceptual Practice

PMDC Verified Question 297 of 494

How do the open-circuit voltage ($ V_{\text{oc}} $) and short-circuit current ($ I_{\text{sc}} $) of a photovoltaic solar cell vary as the incident light intensity $ \Phi $ increases?

Both Voc and Isc increase strictly linearly

Isc increases linearly, while Voc increases logarithmically and saturates

Voc increases linearly, while Isc remains strictly constant

Both parameters decrease exponentially

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

Propolis Cognitive Error Autopsy

Official Correct Choice:

Option B: Isc increases linearly, while Voc increases logarithmically and saturates

Concept:

Short-circuit current $ I_{\text{sc}} $ is directly proportional to the photon absorption rate (light intensity), while open-circuit voltage $ V_{\text{oc}} $ depends logarithmically on the ratio of photo-current to dark saturation current.

Formula:

$$I_{\text{sc}} \approx I_L \propto \Phi$$

$$V_{\text{oc}} = \frac{k T}{q} \ln\left(\frac{I_{\text{sc}}}{I_0} + 1\right) \propto \ln(\Phi)$$

Solution:

Increasing light intensity generates more electron-hole pairs per second, causing $ I_{\text{sc}} $ to increase linearly with $ \Phi $.

Because $ V_{\text{oc}} $ is logarithmic in $ I_{\text{sc}} / I_0 $, it rises quickly at low light levels and then flattens out, saturating near the built-in barrier potential.

Why other options are incorrect:

Option A: $ V_{\text{oc}} $ increases logarithmically, not linearly.
Option C: $ I_{\text{sc}} $ increases with illumination rather than remaining constant.
Option D: Both parameters increase with higher light intensity.

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