OPTIMIZED CELLS (FIGURE 2B-D)

We have studied cells with different construction techniques, using CNT electrodes from the same batch. Similar techniques were employed for data analysis as above (figure 4, table 2). The power transfer curves (figure 4b) show a peak power transfer P at R = R. Gold Guard Ring. The presence of the gold guard ring increases ISC by a factor ~2.5, while VOC remains approximately constant. R is lower by ~3.5 and P is ~2 times greater. Graphite Counter Electrode. Both VOC and ISC are greater than the normally constructed cell and P is ~12 times greater. Thin Cell. When

max

Подпись: 250
image017
image018
Подпись: 150
Подпись: 100
Подпись: 200

image022Load voltage (mV)

Load resistance (Q)

FIGURE 3: Electrical characteristics of the CNSCs. The extracted parameters are presented in table 2. a) I-V characteristics of the cells as indicated. b) Power delivered to the load for all cells as described in the legend for a).

the enriched side is facing the incident solar radiation (“up”), the power is slightly larger than when the regular side is facing the incident radiation (“down”). Both VOC and ISC are lower by factors of ~5 and ~3, which in itself is undesirable. However, optimum power transfer occurs at a much lower resistance.

TABLE 2: Optimized CNSCs.

Cell Type

Voc

Isc

Pmax

Rmax

mV

nA

nW

MQ

Normal Construction

102.7

93.7

5.59

2.85

Gold Guard Ring

129.5

249.5

10.46

0.81

*

Graphite Counter Electrode

438.1

733.2

65.48

0.94

X

Thin Semiconducting Side Up

22.0

38.3

0.22

0.47

+

Thin Semiconducting Side Down

20.9

32.0

0.20

0.58

3.2 DISCUSSION