Explore Module
Brainstorming activities in the classroom
Leading question. Without light, there is no photovoltaic current: what happens to photons as they enter the solar cell, and how do they generate an electrical signal that can power devices?
Prompting questions
What determines whether a photon can generate electricity in a solar cell?
The photon's energy must exceed the semiconductor's bandgap; silicon's bandgap (~1.1 eV) means only photons with wavelengths shorter than ~1100 nm (visible and near-infrared light) can free electrons and generate current.
The photon's energy must exceed the semiconductor's bandgap; silicon's bandgap (~1.1 eV) means only photons with wavelengths shorter than ~1100 nm (visible and near-infrared light) can free electrons and generate current.
Why can't we use all the sunlight that hits a solar panel?
Because photons with energy below the bandgap pass through without generating charge carriers, while photons with much higher energy waste excess energy as heat. This is why single-junction silicon cells have a theoretical maximum efficiency of ~33% (Shockley-Queisser limit).
Because photons with energy below the bandgap pass through without generating charge carriers, while photons with much higher energy waste excess energy as heat. This is why single-junction silicon cells have a theoretical maximum efficiency of ~33% (Shockley-Queisser limit).
Does the solar cell "store" electricity like a battery?
No; the solar cell generates current only when illuminated. The photovoltaic effect produces charge separation and flow in real-time; to store energy, an external battery or capacitor is needed.
Why do some solar panels work better in direct sunlight than in shade?
Because light intensity (photon flux) directly affects the number of electron-hole pairs generated. Lower intensity means fewer photons, fewer charge carriers, and reduced current output. Voltage remains relatively stable, but current drops significantly.
Because light intensity (photon flux) directly affects the number of electron-hole pairs generated. Lower intensity means fewer photons, fewer charge carriers, and reduced current output. Voltage remains relatively stable, but current drops significantly.
Micro-task.
Label the layers of a solar cell (anti-reflective coating, N-type silicon, P-N junction, P-type silicon, back contact) using a worksheet or an interactive diagram.
Suggested resource: Solar Cell Structure Diagram - Encyclopædia Britannica
https://www.britannica.com/technology/solar-cell
Label the layers of a solar cell (anti-reflective coating, N-type silicon, P-N junction, P-type silicon, back contact) using a worksheet or an interactive diagram.
Suggested resource: Solar Cell Structure Diagram - Encyclopædia Britannica
https://www.britannica.com/technology/solar-cell