Operation Module

Basic Level

Understanding the photovoltaic conversion process can be deepened through a series of practical activities that allow students to observe both quantum and electrical phenomena involved in solar energy capture. The aim of this section is to apply, in a guided way, the concepts of photon absorption, charge separation, and current generation studied in the theoretical part, connecting the physics of semiconductors with real-world energy systems.

When light strikes a semiconductor material, photons with sufficient energy excite electrons from bound states into mobile charge carriers-a quantum phenomenon invisible to direct observation but measurable through electrical instruments. Students can observe this behavior using a simple experiment: connect a small solar cell to a multimeter and expose it to different light sources (sunlight, LED lamp, flashlight). As light intensity increases, current rises proportionally, while voltage remains relatively stable. This direct measurement illustrates how photon flux translates into electrical output.

Through the simulation, students can observe energy band diagrams, apply doping to create N-type and P-type regions, and visualize how the P-N junction generates a built-in electric field. When light is introduced, students see electron-hole pairs generated and separated by the junction field, producing current flow. This activity helps students understand how doping and junction physics enable directional charge transport-the foundation of photovoltaic operation.

From these observations arise essential questions: What is the relationship between photon energy and electron excitation? Why does doping create an internal electric field without external voltage? Comparing the simulated semiconductor with real solar cell structure clarifies how material engineering at the atomic scale determines macroscopic electrical performance. 

The focus then shifts to the layered architecture of solar cells. Students analyze the arrangement of functional layers-anti-reflective coating, N-type emitter, P-N junction, P-type base, metal contacts-and their complementary roles:

• The anti-reflective coating maximizes photon entry by reducing surface reflection
• The thin N-layer captures electrons generated near the surface
• The P-N junction creates the electric field that separates charge carriers
• The thick P-layer absorbs longer-wavelength photons deeper in the material
• Metal contacts collect and conduct current to external circuits

The class discussion continues by analyzing cell behavior under varying light conditions. Why does current output change dramatically with shading while voltage remains relatively stable? The answer lies in the direct proportionality between photon flux and charge carrier generation. This collective reflection helps students understand how solar system design must account for partial shading, orientation, and time-of-day variations. 

Students are then invited to compare solar cells with everyday energy devices:

• Solar calculators: low-power applications where small cells provide sufficient energy
• Rooftop panels: series-connected cells generating household-scale power
• Grid-scale solar farms: megawatt installations with inverters, transformers, and storage systems
• Space satellites: high-efficiency multi-junction cells where reliability and weight are critical

Through this analogy, photovoltaics is reinterpreted as a quantum-to-grid energy conversion chain connecting atomic physics, materials engineering, and electrical systems.

Advanced Level

The advanced level deepens the connection between photon absorption and the flow of electrical current through external circuits. Students observe how light energy is converted into separated charges within the P-N junction and how these charge carriers propagate through the semiconductor and metallic contacts to deliver power.

To understand the sequence of events, the concept of band bending at the P-N junction is introduced: when N-type and P-type regions contact, electrons diffuse from N to P and holes diffuse from P to N until an equilibrium is reached. This creates a depletion region depleted of mobile carriers, with fixed positive charges on the N-side and fixed negative charges on the P-side. The resulting electric field (~10⁵ V/cm) is strong enough to separate photo-generated electron-hole pairs before they recombine.

The propagation of charge carriers and the generation of electrical current is illustrated through an Augmented Reality simulation developed with Delightex Studio – Spaces (Marker):
https://edu.delightex.com/Studio/Spaces

Using mobile devices, students explore a three-dimensional model of a solar cell:

1. Observe photons striking the surface and penetrating the semiconductor
2. Visualize electron-hole pair generation when photon energy exceeds the bandgap
3. Follow electrons swept toward the N-layer and holes toward the P-layer by the junction field
4. See electrons flowing through the external circuit (wire, load, return path)
5. Track the complete current loop from generation to load and back

During the activity, guiding questions are proposed:
– At what point in the cell does light become separated electrical charges?
At the P-N junction, where the built-in electric field separates photo-generated electrons and holes before they recombine.

– Why does current flow through the external circuit when the cell is illuminated?
Because the junction continuously generates a voltage difference (photovoltage) between the N-side and P-side, driving electrons through the circuit to minimize the potential difference.

– How does the solar cell produce power without consuming fuel or moving parts?
By directly converting photon energy into charge separation through quantum absorption, then extracting those separated charges as current through metallic contacts-a solid-state energy conversion with no mechanical or chemical transformations.

Answers emerge through group discussion and comparison between quantum-scale carrier generation and macroscopic electrical measurements.

The lesson ends with a reflection on the evolution of photovoltaic technology. Students compare first-generation crystalline silicon cells with emerging technologies:

Activities

The concluding activities aim to consolidate learning and encourage peer collaboration.