Environmental Engineering Reference
In-Depth Information
device structure. The aim of this work is to experimentally observe
whether the impurity PV effect is contributing to charge carrier
creationinthesedevices.TheIPCEmeasurementsshowasharpcut-
offat
∼
740nm,indicatingthatthereisnocollectionintheIRregion.
Accordingtothesemeasurements,thereisnocontributionfromthe
impurity PV effect in these devices.
8.4 Responsivity Measurements
The above measurements clearly raised an issue of disagreement
betweenthetheoreticallyexpectedimpurityPVeffectandtheexper-
imentallyobservednullresults.Thisencouragedthere-examination
of the ways of data collection, analysis, and presentation of IPCE
results, and it was found that there are grey areas which are not
clear to the experimentalists. For this reason, a straightforward
measurement of responsivity as a function of wavelength was
explored. The responsivity of a device is defined as:
Responsivity (A/W)
=
Electrical output of the solar cell (A)/
Light input to the solar cell (W)
This method is fully transparent to the experimentalist and
removes all complications in data collection, analysis, and graphical
presentation. The two required parameters, light input and the
current output, are measured and plotted directly without further
processing of experimental data.
Figure8.2shows atypical measurement, andthemainspectrum
shows similar losses in UV and IR ends as observed in IPCE
measurements. However, the collection in the IR region, up to
∼
1,200 nm, is clearly observed in these measurements. This is a
strong indication that during IPCE data collection, analysis, and
graphical presentations, this useful informationis completely lost.
8.5 I-V Measurements Under Dark Conditions
ThepositiveindicationofexistenceofimpurityPVeffectencouraged
further investigation of this effect using other techniques. The most
