Question 1

How do dye-sensitized solar cells differ from conventional silicon solar cells?

Accepted Answer

Dye-sensitized solar cells separate light absorption from current transmission, reducing electron-hole recombination. Unlike silicon cells, they produce consistent power at high temperatures and steep light angles, yielding nearly 50% more power under low light conditions. They are easier to manufacture and can use abundant plant-based pigments as dyes instead of expensive materials.

Question 2

What happens when a photon excites an electron in a semiconductor?

Accepted Answer

When a photon with bandgap energy strikes an electron, the electron is promoted to the conduction band, leaving a hole in the valence band. Both the electron and hole can be conducted from atom to atom until they recombine. In dye-sensitized cells, the excited dye electron is immediately injected into the semiconductor's conduction band, preventing recombination.

Question 3

What are the main components of a dye-sensitized solar cell?

Accepted Answer

A dye-sensitized solar cell contains a sensitizer dye, a mesoporous semiconductor layer like anatase TiO2, an organic iodide electrolyte, and two electrodes. The photoelectrode collects electrons from the excited dye, while the counter-electrode, typically platinum or carbon, completes the circuit. This configuration allows efficient charge separation and current generation.

Question 4

Why are plant-based pigments useful for dye-sensitized solar cells?

Accepted Answer

Plant-based photosensitive pigments such as carotenoids and anthocyanins are abundant, practical, and inexpensive compared to organic ruthenium complexes. While less efficient than synthetic dyes, they respond across the visible spectrum and enable rapid prototyping of cells with novel dyes. Their natural availability makes them ideal for affordable, scalable solar cell fabrication.

Question 5

What information does a current-voltage curve reveal about solar cell performance?

Accepted Answer

A current-voltage curve describes solar energy conversion efficiency and identifies three key performance points. The open circuit voltage is where the curve crosses the x-axis at maximum voltage with zero current. The maximum power point occurs at the curve's knee, providing ideal voltage and current conditions. These metrics allow comparison of different solar cell designs.

Question 6

How can dye-sensitized solar cells be used for light harvesting applications?

Accepted Answer

Dye-sensitized solar cells yield high power under low light, making them valuable for harvesting indoor light to power sensors, ID tags, and data transmitters. Developing dyes that introduce energy levels within the bandgap enables electrons to upconvert into the conduction band. This approach has doubled photon-to-electron conversion in near-infrared wavelengths by replacing single high-energy absorption with two lower-energy absorptions.

Question 7

What fabrication techniques improve dye-sensitized solar cell performance and transparency?

Accepted Answer

Electrospinning injects a TiO2 slurry into an electric field to produce nanofibers for high-performance electrodes. Inkjet printing deposits electrodes on glass substrates, achieving cell efficiencies of 3.5%. For photovoltaic windows, TiO2 hollow glass microspheres are added to electrodes to minimize pollution while maintaining output, enabling affordable manufacturing of transparent solar devices.

Celle di Grätzel (Dye-sensitized Solar Cells) - Quiz di valutazione