Electrical characterization of photovoltaic materials and solar cells
Electrical characterization of
photovoltaic materials and
solar cells
by Josef W. Flossmann, Keithley Instruments GmbH, Germering, Germany
Some of the electrical tests commonly Electrical characterization is important
The increasing demand for
performed on solar cells involve measuring in determining how to make the cells as
clean energy and the largely
current and capacitance as a function efficient as possible with minimal losses.
untapped potential of the sun as
of an applied DC voltage. Capacitance Instrumentation such as the Model
an energy source is making solar
measurements are sometimes made as 4200-SCS Semiconductor Characterization
energy conversion technology
a function of frequency or AC voltage. System can simplify testing and analysis
These measurements are usually performed when making these critical electrical
increasingly important. As a
at different light intensities and under measurements. The Model 4200-SCS is an
result, the demand for solar cells,
different temperature conditions. A integrated system that includes instruments
which convert sunlight directly
variety of important device parameters for making I-V and C-V measurements,
into electricity, is growing.
can be extracted from the current-voltage as well as control software, graphics,
Solar or photovoltaic (PV) cells (I-V) and capacitance-voltage (C-V) and mathematical analysis capability.
are made up of semiconductor measurements, including output current, The Model 4200-SCS is well-suited for
materials that absorb photons
conversion efficiency, maximum power performing a wide range of measurements,
from sunlight and then release
output, doping density, resistivity, etc. including current-voltage (I-V), capacitance-
electrons, causing an electric
current to flow when the cell
Subsite Level Test Description
is connected to a load. A Module
variety of measurements are
IV_sweep fwd-ivsweep Performs I-V sweep and calculates I
sc
, V
oc
, Pmax, Imax, Vmax, FF
used to characterize a solar
rev-ivsweep Performs reversed bias I-V sweep
cell’s performance, including its
CV_sweep cvsweep Generates C-V sweep
output and its efficiency. This
C-2vsV Generates C-V sweep and calculates 1/C
2
electrical characterization is
cfsweep Sweeps the frequency and measures capacitance
performed as part of research
DLCP Measures capacitance as AC voltage is swept. DC voltage is
and development of photovoltaic
applied so as to keep the total applied voltage constant. The
cells and materials, as well
defect density is calculated.
as during the manufacturing
4PtProbe_ HiR Uses 3 or 4 SMUs to source current and measure voltage
process.
resistivity difference for high resistance semiconductor materials.
Calculates sheet resistivity.
LoR Uses 1 or 2 SMUs to source current and measure voltage
using remote sense. Calculates sheet resistivity. Uses current
Keywords: Testing, Analysis,
reversal method to compensate for thermoelectric voltage
Solar Cells, I-V, C-V, C-f,
offsets.
DLCP, Resistivity, Hall Voltage
vdp_resistivity I1_V23 First of 4 ITMs that are used to measure the van der Pauw
resistivity. This ITM sources current between terminals 1 and
4 and measures the voltage difference between terminals 2
and 3.
I2_V34 Sources current between terminals 2 and 1 and measures the
voltage difference between terminals 3 and 4.
I3_V41 Sources current between terminals 3 and 2 and measures the
voltage difference between terminals 4 and 1.
I4_V12 Sources current between terminals 4 and 1 and measures the
voltage difference between terminals 1 and 2.
Table 1. Test modules in the SolarCell project
30 – Global Solar Technology – October/September 2009
www.globalsolartechnology.com
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