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Georgia Institute of Technology
School of Electrical and Computer Engineering
ECE 3080: Semiconductor Devices
Homework #5: Optoelectronic Devices
1. A silicon solar cell consists of an ntype emitter and a ptype base. The goal of this problem is to
determine the optimum base doping in order to maximize efficiency. Assume that the generation
rate is constant throughout the problem, and equal to the generation rate 150
µ
m into the solar cell.
You may assume that the saturation current is that of an ideal diode. The properties of the solar cell
are shown below.
N
D
= 1
×
10
19
cm
3
τ
p
= 0.1
µ
sec D
p
= 0.5 cm²/sec
x
e
= 2.5
µ
m
N
A
= ??? cm
3
τ
n
= ??
µ
sec D
n
= 50 cm²/sec
x
b
= 300
µ
m
(a)
The incident power density is 90 mW/cm². Calculate the generation at 150
µ
m, using an
absorption coefficient of 100 cm
1
at a wavelength of 826.67 nm.
(b)
The relationship between doping and lifetime is shown below. What is the optimum doping
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This note was uploaded on 08/28/2010 for the course ECE 3080 taught by Professor Staff during the Fall '08 term at Georgia Institute of Technology.
 Fall '08
 Staff

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