it seems a pn or p-i-n junction is missing then

Apologies for the oversight. You are correct, in a traditional PV cell, a p-n junction or p-i-n junction is indeed a crucial component. Here's an amended explanation:

In addition to the layers mentioned earlier, a p-n or p-i-n junction is an essential part of a conventional photovoltaic (PV) cell. This junction is formed by two semiconductor layers with different doping types: p-type (positively charged) and n-type (negatively charged).

1. Transparent Front Electrode: This layer remains the same as previously explained, serving as a transparent conductive material for electrical conductivity while allowing light transmission.

2. Antireflection Coating: The antireflection coating's purpose also remains unchanged - reducing light reflection, maximizing absorption, and minimizing surface losses.

3. Semiconductor Absorber Layer: This layer is typically a single crystal or polycrystalline semiconductor material, such as silicon (Si). It contains the p-n or p-i-n junction, where the energy conversion occurs. The doping of the semiconductor layers creates an electric field at the junction.

• In a p-n junction, the p-type and n-type regions form a depletion region. When photons from sunlight strike this region, electron-hole pairs are generated due to the absorbed energy. The electric field within the depletion region separates these charges, creating a voltage difference.

• In a p-i-n junction, an intrinsic (i) layer is inserted between the p-type and n-type layers. This layer widens the depletion region and improves the cell's efficiency by reducing recombination losses.

4. Back Contact: Similar to the previous explanation, the back contact allows for the collection of the generated electrons and facilitates their flow out of the cell.

5. Back Reflector: The role of the back reflector, which enhances light trapping and absorption, remains the same.

6. Back Encapsulation: The protective back encapsulation layer also remains unchanged, safeguarding the cell from moisture and external damage.

The p-n or p-i-n junction is a crucial element in the PV cell, enabling the separation and collection of photo-generated charges, which leads to the conversion of light energy into electrical energy.