Question

For Photovoltaic Power Generation: A. Electric field separates charges
B. Photon energy exceeds bandgap
C. Electron-hole pair generated
D. DC output obtained
Choose the correct answer from the options given below:

• A. C, B, A, D
• B. C, B, D, A
• C. B, C, A, D
• D. B, C, D, A

Hint:

Photovoltaic process sequence: \[ \text{Photon Absorption} \rightarrow \text{Electron-Hole Generation} \rightarrow \text{Charge Separation} \rightarrow \text{DC Output} \] This sequence is extremely important for theory and viva examinations.

Answer 1

The Correct Option is C

Concept: Photovoltaic power generation converts solar energy directly into electrical energy using semiconductor materials. The photovoltaic effect involves several sequential physical processes occurring inside a solar cell.

Step 1: Photon Energy Must Exceed Bandgap
The first requirement for photovoltaic action is that incident photon energy must be greater than the semiconductor bandgap energy. Mathematically: \[ E_{photon} > E_g \] where:
• \(E_{photon}\) = energy of incoming photon
• \(E_g\) = bandgap energy Without sufficient energy, electrons cannot move to the conduction band. Thus, the first process is: \[ B \]

Step 2: Generation of Electron-Hole Pair
When the photon energy exceeds the bandgap energy, electrons absorb energy and jump from valence band to conduction band. This creates:
• Free electron
• Hole Thus, electron-hole pairs are generated. Therefore, second process is: \[ C \]

Step 3: Separation of Charges
The built-in electric field present at the p-n junction separates the generated charge carriers.
• Electrons move toward n-side
• Holes move toward p-side This separation prevents recombination and establishes current flow. Hence, third process is: \[ A \]

Step 4: DC Output is Obtained
Due to directed movement of charges, a direct current output is produced from the solar cell. Solar cells naturally generate DC power. Thus, final process is: \[ D \]

Step 5: Correct Sequence
The complete sequence is: \[ B \rightarrow C \rightarrow A \rightarrow D \] Therefore, correct answer is: \[ \boxed{(C)\ B,\ C,\ A,\ D} \]