Given below are V versus I graphs for different types of p-n junction diodes marked A, B, C, and D.

The correct sequence of graphs corresponding to forward biased p-n junction; Zener diode; Photo diode and Solar cell in order is ______.

The correct sequence of graphs corresponding to forward biased p-n junction; Zener diode; Photo diode and Solar cell in order is (A), (C), (B), (D).

1. Forward Biased p-n Junction Diode - Graph (A)
Under forward bias, a p-n junction diode conducts current easily. Graph (A) shows the current-voltage behavior of the diode under biasing conditions.

2. Zener Diode - Graph (C)
A Zener diode is specifically designed to operate in the reverse breakdown region. Graph (C) clearly shows the characteristic breakdown voltage labeled as:

$V_Z$

in the negative voltage (reverse bias) region, which is the defining signature of a Zener diode.

3. Photo Diode - Graph (B)
A photo diode is operated in reverse bias to detect light. Graph (B) shows the characteristic curve depicting the short-circuit current:

$I_{\mathrm{sc}}$

and open-circuit voltage:

$V_{\mathrm{oc}}$

under illumination.

4. Solar Cell - Graph (D)
A solar cell generates voltage and current when light falls on it. Graph (D) illustrates the standard current-voltage relationship representing the photo-generated current.

Therefore, matching each device with its corresponding graph in the given order yields the sequence: (A), (C), (B), (D).