Early photovoltaic cells were based on silicon containing traces of other elements. State the type of semiconductor produced by doping silicon with indium, In, giving a reason that refers to its electronic structure.

Dye-sensitized solar cells, DSSCs, use a dye to absorb the sunlight. State two advantages that DSSCs have over traditional silicon based photovoltaic cells.

The structure of two dyes used in DSSCs are shown.

Predict, giving a reason, which dye will absorb light of longer wavelength.

p-type AND has 3 «valence» electrons

OR

p-type AND fewer electrons «than silicon»

Do not accept “it is in group 3/13” as reason.

[1 mark]

Any two of:

cheaper

OR

ease of fabrication

use light of lower energy/lower frequency/longer wavelength

absorb wider range of wavelengths

dye converts most/all absorbed photons into electrons

plentiful /renewable resources «to construct DSSC cells»

operate at lower «internal» temperatures/better at radiating heat away «since constructed with thin front layer of conductive plastic compared to glass box in photovoltaic cell»

use of nanoparticles provides large surface area exposure to sunlight/sun/light

can absorb better under cloudy/low light conditions

better conductivity

more flexible

[2 marks]

B AND has greater/more «extensive» conjugation

Accept “more alternating single and double bonds”.

[1 mark]