Page 85 - Applied Photovoltaics

6. Application and firing of aluminium onto the rear surface.
7. Electroless plating of front and rear contacts simultaneously (Ni-Cu-Ag).

8. Edge isolation.
An improved process for the BCSC was developed in 1993, which is capable of
higher efficiencies at lower cost. The primary differences are the use of boron-
diffused grooves at the rear and elimination of the aluminium deposition and firing
steps (Honsberg et al., 1993).

EXE RCI S ES

4.1 (a) Give an overview of techniques currently used for silicon substrate
formation.
(b) What are the advantages and disadvantages of each?

(c) Do crystalline silicon substrates have a long-term future?
4.2 (a) What substrate materials, other than silicon, can solar cells be made
from?
(b) What are the advantages and disadvantages of each?
(c) Are some substrate materials better suited to specific applications or
environments compared to others?
4.3 In block diagram form, outline the processing steps required to convert
quartzite into a silicon space cell.

4.4 (a) Draw the cross-section of a typical commercial solar cell, marking
relevant parts.
(b) Briefly describe how a solar cell operates.

(c) Outline important aspects of solar cell design that affect efficiency.
4.5 Commercially mass-produced solar cells for terrestrial applications have
always had significantly lower generating efficiencies than the best laboratory
fabricated cells. Discuss the reasons for and the effects of the differences in
approaches and processing techniques between the two environments, and
explain why these lead to such different levels of performance.
4.6 A certain technology produces 10% efficient solar modules at a cost of $1 per
2
peak watt output under bright sunshine (1 kW/ ). In a particular application,
those balance-of-system costs that depend on the area of the array deployed
2
amount to $80/m . Assuming that other costs are identical in each case, at
what price would 5% efficient modules produced by a second technology
have to sell to give similar overall system costs?

4.7 (a) Derive an expression for the fractional power loss due to lateral
current flow in the diffused top layer of a silicon solar cell.

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