general

Question 1

What does it mean to dope a semiconductor?

Answer 1

Doping the intentional introduction of impurities into an intrinsic semiconductor to modulate its electrical properties.

Question 2

What do fourth generational solar cells combine?

Answer 2

The low cost and flexibility of conducting polymer films (organic) with the lifetime stability of novel nanostructures (inorganic).

Question 3

What are fourth generational solar cells?

Answer 3

Solar cells based on organic-inorganics, offering improved power conversion efficiency over 3rd generational solar cells, whilst maintaining their low cost base.

Question 4

Why are active inorganic nano-materials incorporated into 4th generational solar cells?

Answer 4

To improve the harvesting of solar energy and the manipulation of electrical charges, enhancing efficiency and lifetime stability.

Question 5

How could the properties of hybrid organic-inorganic solar cells possibly be tailored?

Answer 5

By varying the sizes of the nano-particles (the quantum size effect).

Question 6

How are hybrid organic-inorganic solar cells prepared?

Answer 6

By inexpensive, wet chemical synthesis.

Question 7

What are the advantages of hybrid organic-inorganic solar cells?

Answer 7

• Cost effective.
• Efficient electron transportation.
• Strong optical absorption.
• Efficient exciton dissociation.

Question 8

What does the photoeffective layer consist of in hybrid organic-inorganic solar cells?

Answer 8

Interconnected, semiconducting nanoparticles in a solid semiconducting polymer phase.

Question 9

Why does a large bandgap result in larger open circuit voltage?

Answer 9

It causes a large potential barrier.

Question 10

Why does a small bandgap result in a large short circuit current?

Answer 10

Because many photons will create electron hole pairs.

Question 11

What is the dilemma when selecting a material based on bandgap?

Answer 11

P=VI
A small bandgap results in a large short circuit current, whilst a large bandgap results in a large open circuit voltage.

Question 12

What is the ideal bandgap?

Answer 12

Usually around 1.5eV

Question 13

What does the ideal bandgap size depend on?

Answer 13

The solar spectrum.

Question 14

What are the five assumptions limiting solar efficiency?

Answer 14

• Single bandgap energy.
• One e- h+ pair per photon.
• Non-use of sub band gap photons.
• Single population of each charge carrier type.
• One-sun incident intensity.

Question 15

What device principles are used to overcome the “non-use of sub-bandgap photons” efficiency limitation?

Answer 15

Up conversion.

Question 16

What device principles are used to overcome the “one-sun incident intensity” efficiency limitation?

Answer 16

Concentrator solar cells.

Question 17

What device principles are used to overcome the “single population of each charge carrier type” efficiency limitation?

Answer 17

• Hot carrier solar cells.
• Intermediate band solar cells.
• Quantum well/dot solar cells.

Question 18

What device principles are used to overcome the “one e- h+ pair per photon” efficiency limitation?

Answer 18

• Down conversion.
• Multiple exciton generation.
• Avalanche generation.

Question 19

What device principles are used to overcome the “single band gap energy” efficiency limitation?

Answer 19

• Multi-junction solar cells.

- Quantum dot/well solar cells.

Question 20

What 5 solar cells are the paths to ultra-high conversion efficiencies?

Answer 20

• Multi-junction cells.
• Multiple absorption path cells.
• Multiple energy level cells.
• Multiple spectrum cells.
• Multiple temperature cells.

Question 21

What is theoretical efficiency limit for multijunction solar cells utilising other high efficiency approaches?

Answer 21

> 80%

Question 22

What happens when module temperature increases?

Answer 22

Efficiency decreases so the module must be cooled by natural ventilation.

Question 23

What can be done to increase open circuit voltage?

Answer 23

• Increase bandgap.
• Increase doping.
• Increase minority carrier diffusion length.
• Decrease Sr.

Question 24

What can be done to increase short circuit current?

Answer 24

• Reduce bandgap.
• Reduce reflection.
• Increase minority carrier diffusion length.
• xj at optimal level.

Question 25

What can be done to increase fill factor?

Answer 25

• Decrease series resistance.
• Increase doping.
• Use a thick emitter.