Original Author: Prof. Niall Tait
Modified by Prof. Ravi Prakash
Updated for ELEC 4703 Winter 2022 by Robert Gauthier
ELEC 4703 LAB 4
SOLAR CELL TESTING: PART 1
OVERVIEW
In this lab we will begin testing the solar cells designed by the current 4703 class. The cell
characteristics will be measured using an HP4145 Semiconductor Parameter Analyzer.
CONNECTION TO THE REMOTE SERVER
I.
Start by connecting to the Carleton VPN as done in Labs 1, 2 and 3. For detailed instructions
II.
please refer to the Lab 1, 2 or 3 tabs in Brightspace
III.
Once connected to the Carleton VPN, open labstats on your browser using the link:
https://remoteaccess.labstats.com/Carleton-University-Electronics-Engineering-me4135. Under
the heading ME4135, all the available lab stations are shown.
For the 8 lab groups, we have set up stations (7-14) and below is the breakdown of groups and
their corresponding stations.
Lab group Station number
7
7
8
8
9
6
10
1
11
2
12
3
13
4
14
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IV.
V.
Find your above assigned lab station and click on the connect button. Only one user will connect
to the lab station using the procedure above; the other group members will participate in all lab
activities interactively through group discussion and multiple user screenshare features on BBB.
Once you click the connect button, you will be asked to download a file, click on the download
button. If your lab station is not shown, it means that the lab station is currently in use already or
the previous user did not sign out correctly. If this is the case, alert the TA in the lab and they
will reset the station for you.
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VI.
Open the downloaded file, which will be named the same as the assigned lab station number.
You will be shown the following screen, click on connect.
You will then be asked to enter your credentials. You must enter “VLSI\” before your username
(same as your MC1 username) and the password is “pW” followed by your student number.
Click on OK.
You will be asked to confirm that you would like to connect. Click on “Yes” and you will
connect to the lab station.
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VII.
Getting started with IntuiLink Data Capture: Perform a quick search by typing IntuiLink in the
Windows search bar.
VIII.
Click the instruments tab from the top menu and select 4145A/B.
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IX.
To log into the instrument, you should ensure that the instrument addresses is selected as: GPIB
17.
Make sure to save all work on your H: drive to avoid any data loss.
Before starting the lab, read through the rest of this instruction
manual.
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INTRODUCTION TO THE SOLAR TEST PROBE STATIONS
Before you begin testing anything, please familiarize yourself again with the probe stations
(Figure 1). These stations include an incandescent lamp with a high temperature tungsten-halogen
bulb intended to simulate sunlight, and a temperature-controlled chuck. The lamp is pre-
calibrated for you so that the input spectral power density to the cell would be
(Hin) 100 mW/cm2. We will see that temperature control is essential to obtain an accurate
measurement of Voc. The middle and bottom gray/black buttons on the temperature controller
respectively raise and lower the set-point temperature.
Stage cooler
power supply
Lamp
Temperature
controller
Vacuum Pump
Chuck/Stage
SMU Cables
Probe positioner/
Micromanipulator
Figure 1: Carleton solar cell probe station
CELL TESTING
In order to test a cell, we need to create electrical contacts with the front metal grid and the back
contact. The polished chuck acts as the back contact. The front contact is achieved by
positioning a fine tip micro-positioner probe onto the busbar contact pad. Figure 2 shows a closer
look at the micromanipulator and probe. For all experiments, a TA will setup the front and back
contact of each cell.
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Figure 2. Closer view of the SMU connection and the micromanipulator.
GETTING STARTED
Our Lab TA would have pre-loaded the program solar1 on the HP4145. This program will produce
a simple solar cell I-V curve, with the emitter bias on (SMU 1) set to sweep from 0 to -0.7V. SMU 2
is set as common and is connected to the chuck (base). Click the camera icon to access the webcam
feed to step through the menus until the graphics data display page appears. The TAs will
essentially setup all manual data capture steps, which you can observe through the camera feed.
Cell setup: One of the TAs will place a wafer piece that we want to test and locate your group’s cell.
Using tweezers, they will center the piece on the chuck and turn on the backside vacuum. The
chuck temperature controller will be turned on and set to 25°C.
Under Solar 1 configuration, SMU1 sources voltage VEE and reads current IEE. The chuck to SMU2,
which applies a common ground reference voltage to the base. The lamp is set on to the brightest
setting (“II”) and calibrated to give an incident light power density of approximately 100
mW/cm2 at the chuck surface, equivalent to the light power density of AM1.5 sunlight.
1. ILLUMINATED I-V CHARACTERISTICS
Using the HP4145 record the illuminated I-V curve (IEE versus VEE) for your AR-coated cell.
Capture the curve with IntuiLink Data Capture and include it in your final report. The assisting TA
will turn on the cursor/marker function in the 4145, to accurately identify values of Voc, Isc, Vmp and
Imp, and label these on your graph. Compute FF and Jsc. Compute the energy conversion efficiency η.
2. EFFECT OF ANTIREFLECTION COATING
At this point, the setup will switch to a cell of your design without AR coating. Use a quarter from
the same wafer tested in Part 1. Record the IEE-VEE curve IntuiLink Data Capture and include it in
your final report. Determine Voc, Isc and Jsc and η. What percentage improvement in Jsc is provided
by the antireflection coating? How does this compare to the predictions of Lab 3 section 3?
Looking at it from the webcam, what color does the AR coated cell appear? Why does it appear to
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have that color? Hint: Think constructive interference for reflected wavelengths.
3. THE SUPERPOSITION PRINCIPLE
The Superposition Principle states that the current IL flowing in an illuminated solar cell at a bias
voltage V is given by:
IL(V) = ID(V) + Isc
(1)
where ID is the dark current and Isc is the short circuit photocurrent.
To verify this, we will switch back the test cell to your group’s AR coated cell. Once the setup is
ready, record the IEE–VEE curve under illumination. and store the curve (This will be done by
pressing the grey soft key > Store). Write down the value of Isc. Next completely cover the cell with
a black cloth. Program the HP4145 to compute ISUP = IEE + Isc. Record the ISUP versus VEE
curve. Using the recall feature, compare the ISUP-VEE curve with the actual illuminated I-V curve.
Include the superposed curves in your report. Comment on the accuracy of the superposition
principle. Suggest a reason for any measurable deviation from Equation (1). Does Equation (1)
over or underestimate the energy conversion efficiency of your cell?
4. TEMPERATURE EFFECTS
To observe the effect of temperature on solar cell, you will test your solar cell and record the
illuminated IEE-VEE curve at 20°C and at 40°C. Using the append feature of the HP4145, a graph
with the two curves overlapping can be captured. Include the comparison plot in your final report.
Discuss the effect of temperature on the cell characteristics and efficiency. Briefly explain your
observations in terms of the temperature dependence of the dark current. When finished, we will
return the chuck temperature to room temperature, 25°C.
5. RED AND YELLOW RESPONSE
A yellow light filter will be placed in front of the light source by a TA. Record the IEE-VEE curve
and note the value obtained for Isc. Repeat this measurement again with a red-light filter placed
between the light source and the cell. Can you explain the difference in values of Isc obtained if any
for the unfiltered light vs the yellow light filter vs the red-light filter setup?
DATA REPORTING
A report is not required for Lab 4 since all the testing and characterization data is part of a
final project report on solar cell design, fabrication and testing. For this purpose, at the end
of the lab you are required to prepare a table summarizing all of your results obtained.
This table should include the wafer name, substrate resistivity, emitter sheet resistance, Jsc,
Voc, FF and η. Ensure to distinguish between uncoated and AR coated cells and any cells tested
with the red and yellow filters. TAs will verify this table during Lab check-out.
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