A Step-by-Step Explanation

Photovoltaic Cells: The Building Blocks

Solar panels consist of photovoltaic (PV) cells, typically made from silicon, a semiconductor. These cells convert sunlight directly into electricity through the photovoltaic effect.

Semiconductor Structure: P-N Junction

Doping: Silicon is doped with impurities to create two layers:

N-type layer: Contains extra electrons (e.g., doped with phosphorus).

P-type layer: Contains "holes" (positive charge carriers, doped with boron).

Electric Field: At the P-N junction, electrons diffuse from N-type to P-type, creating an electric field that prevents further diffusion.

Photon Absorption

When sunlight (photons) strikes the cell, photons with energy greater than silicon’s bandgap (1.1 eV) transfer energy to electrons.

This energy knocks electrons loose, creating electron-hole pairs.

Charge Separation

The electric field at the P-N junction pushes free electrons toward the N-side and holes toward the P-side, preventing recombination and creating a voltage potential.

Current Generation

Metal Contacts: Conductive plates on the top and bottom of the cell collect electrons.

When connected via an external circuit, electrons flow from the N-side to the P-side, generating direct current (DC).

Inversion to Usable Power

Inverter: Converts DC electricity into alternating current (AC) for household use.

Grid/Battery Integration: Excess power can be fed back to the grid or stored in batteries.

System Components

Arrays: Multiple cells form a panel; panels are linked into arrays for higher output.

Balance of System (BOS): Includes wiring, mounts, and monitoring systems.

Efficiency Factors

Material: Monocrystalline (high efficiency) vs. polycrystalline (lower cost).

Environmental: Temperature, shading, and panel angle affect performance.

Losses: Photons with insufficient energy or excess energy (lost as heat).

Environmental Impact

Pros: Zero emissions during operation; reduces fossil fuel reliance.

Cons: Manufacturing involves energy use and resource extraction.

Key Considerations

Lifespan: 25–30 years with minimal maintenance.

Cloudy Days: Panels operate at reduced efficiency.

Anti-Reflective Coating: Enhances light absorption.

Summary Flow:

Sunlight → Photons → Electron-Hole Pairs → Charge Separation → DC Current → Inverter → AC Electricity → Power Use/Storage.