I-V Measurement Systems

Features • I-V Measurement System Models • Cell Testing Fixture • Software Features • Examples of I-V Measurement Screens • System Specifications

An I-V Measurement System measures I-V curves of solar cells and calculates critical cell performance parameters including Short circuit current (ISC), Open circuit voltage (VOC), Fill Factor (FF), Maximum current (IMAX), Maximum voltage (VMAX), Maximum power (PMAX), and Efficiency (η) and saves them automatically on hard disk drive. In addition, with optional hardware, cell’s temperature and irradiance level is measured and stored for future analysis. The turn-key system includes rack-mounted electronics and testing chuck. The rack-mounted elecronics includes an industrial computer, LCD monitor, keyboard and mouse (in a storage drawer), electronic load, installed software for I-V Curve testing and cell holder assembly. The software can automatically operate the shutter of most solar systems for ease of use. These sytems are intended for customers who already have a Solar Simulator. Those who plan to purchase a PET Solar Simulator as well, will receive an integrated system, where the cell testing assemly is an integral part of the solar simulator structure. With its wide range and high accuracy of measurement as well as unique software features, the system can be an excellent tool for research applications in a laboratory. It may also be used on a production line as the end-of-line tester/sorter of the manufactured solar cells (SC), with optional software for classifying cells into 16 different catagories. Curves are measured using common four probes (Kelvin) technique. System meets all requirements of the IEC 904-1 standard. FEATURES I-V Measurement System main features are: Measurement of light and dark I-V curves Short measurement time (typically < 500 ms for light measurements) Advanced signal filtering procedure enables I-V measurement under strongly fluctuating light sources (e.g. up to =5%) Calculating cell series resistance according to IEC 60891 standard 3 curve correction to STC procedures implemented Wide range of measured current values (0 Amps up to 20 Amps) 16 bit measurement resolution Procedures enabling fitting of measured I-V curve to either of three equivalent diode models Facilities enabling fast routine determination of thermal coefficients of basic parameters of a solar cell Correction of measured I-V curve to any other conditions than those recorded during the test Advanced, easy to use measurement software

Curve Data Acquisition System Model CC-3 Automated cell contacting Automated cell contacting Please click on images for a larger view.

I-V MEASUREMENT SYSTEM MODELS

CC-1: I-V Curve Data Acquisition System Description and features
An integrated Cell Characterization (I-V Measurement) system with 1A Source Meter (Keithley Model # 2400) with cell temperature control & automated cell contacting.

CC-3: I-V Curve Data Acquisition System Description and features
An integrated Cell Characterization (I-V Measurement) system with 3A Source Meter (Keithley Model # 2420) with cell temperature control & automated cell contacting.

CC-5: I-V Curve Data Acquisition System Description and features
An integrated Cell Characterization (I-V Measurement) system with 5A Source Meter (Keithley Model # 2440) with cell temperature control & automated cell contacting.

CC-15: I-V Curve Data Acquisition System Description and features
An integrated Cell Characterization (I-V Measurement) system (15A Source Meter, designed by our affiliated company), with cell temperature control & automated cell contacting.

CC-20: I-V Curve Data Acquisition System Specification & Technical Description
An integrated Cell Characterization (I-V Measurement) system (20A Source Meter, designed by our affiliated company), with cell temperature control & automated cell contacting.

GENERAL SYSTEM DESCRIPTION

The Solar Cell I-V Curve Data Acquisition System characterizes the current-voltage (I-V) characteristics of photovoltaic devices with currents up to 20.0 amperes. It calculates the solar cell parameters, generates printable test reports and saves test data in text files. Curves are measured using classic four probes (Kelvin) technique. The system includes electronics, software, rack-mount computer, chuck and cell testing fixture with irradiance monitoring and optional temperature control. It interfaces with the customers’ Solar Simulator or a Solar Simulator can be supplied.

   
View of typical IV-Measurement System Consoles

CELL TESTING FIXTURE

The I-V Curve Data Acquisition includes a fixture for holding cell during testing. These fixtures range in sizes to accommodate cells from small to up to 300 mm x 300 mm, larger sizes are available. Adjustable cell stops, in the X & Y-axis, are provided to consistently locate the cells for testing.

Two back-side contacts (one current and one voltage) are embedded in the platen (electrically isolated from the platen) and make good electrical contact when the cell is held down by vacuum to the platen. Both of the bottom voltage and current probes are gold-plated.

Two bus bars with multiple spring loaded contacting probes (20 per bus bar) are mounted on a frame for contacting the front of the cell. The frame can be manually raised to place the cell on the platen for testing. The cell is held down with vacuum during testing (customer needs to supply the vacuum source). After placing the cell in position, the frame can be manually lowered to make probe contact with the cell. Once in the down position, the frame is held down by clasps to maintain contact with the cell.

Optional automatic cell contacting is available upon request. With the fully automated cell contacting, when the user initiates the I-V measurement, the software activates the vacuum to hold the cell, lowers the cell contacting arms and opens the solar simulator shutter to fully automate the I-V measurement of the cells.

Optional provision is available for measuring the intensity of the light and temperature during IV Curve data acquisition to enable the user to correct the IV curve to standard test conditions (STC) or user defined test conditions.

Optional temperature control of the cell is also available. The cell platen can be either cooled or heated in the temperature range of 5-75° C using Peltier cells. Temperature of the platen is measured automatically with accuracy of < ±0.5° C and is monitored during cell measurement.

View of a typical cell measuring table with multiple probes solar cell contacting

SOFTWARE FEATURES

• Easy to use MS Windows environment and user friendly software.
• Software handles measurement of both P type and N type cells without any cell connection changes.
• Advanced noise filtering feature to enable measurement of good quality I-V curves even under fluctuating intensity conditions.
• Light Intensity & Temperature monitoring and control, 0-60°C Standard. Other ranges optional.
• Calculation of cell series resistance according to IEC 60891 standard.
• Procedures for fitting of measured I-V Curve to either equivalent diode models, i.e. SEM-Single Exponential, DEM-Double Exponential and VDEM-Variable Double Exponential with seventeen (17) weight functions.
• Procedures for curve correction to Standard Test Conditions (STC) to IEC 60891, Anderson’s and Blaessar’s or user defined conditions. User has the ability to perform automatic correction of measured I-V curve to STC (Standard Test Conditions), i.e. light intensity and temperature or other conditions specified by the user.
• Computes solar cell parameters including I_SC, V_OC, FF, I_MAX, V_MAX, P_MAX, E_ff , R_s and R_sh and saves them automatically on hard disk drive. In addition cell’s temperature and irradiance level is measured and stored for future analysis.
• Thermal Coefficients of V_oc & P_m.
• Dark saturation current, R_S and R_SH determination.
• Provides printable test reports and test data in text files for easy exchange between programs.
• Software features include cell sorting in various categories. This cell sorting can be performed in production or in virtual binning modes specified by the user.
• Solar Simulator shutter control. (Solar Simulator sold separately)

Majority of the features highlighted in yellow are usually not found in competitors' software.

OPTIONS

Temperature Control
Temperature control of the platen that holds the cell during measurement is available. The standard temperature control range is 0-60°C. Other temperature control ranges are available. Temperature control accuracy is < ±1°C.

Setup and Training
System setup is easy when using the instructions provided in the manual. If desired, PET will provide system setup and training at the customer’s facility.

EXAMPLES OF I-V MEASUREMENT SCREENS

Example of Light Measurement in an IV-Measurement System
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Example of Dark Measurement in an IV-Measurement System
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Example of cell’s series resistance determination according to IEC 60891 Standard in an IV-Measurement System
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Example of cell’s I-V curve fitting to Double Diode equivalent electrical model in an IV-Measurement System
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SYSTEM SPECIFICATIONS

MODEL	CC-1	CC-3	CC-5	CC-15	CC-20
Max. Current Range (A)	±1	±3	±5	±15	±20
Max. Voltage Range (V)	±40	±40	±40	±10	±10
Measurement Resolution	16 Bit
Measurement Accuracy	Better than 0.5%
Measurement Mode	Fixed or Auto
Measurement Time (Light)	< 500ms for stable light (Up to 4s if filtering for light fluctuations required)
Measurement Time (Dark)	100-1,000ms
Maximum Points per Curve	100-1,000 (model specific)
Maximum Data Acquisition Speed	100kHz			4,096
Maximum Cell Throughput	1,200/Hour (With optional Robotics)
Phase (Power)	Single Phase
Voltage (Volts)/Frequency (Hz)	220VAC (115VAC Optional)/50-60Hz
Max. Power Consumption (W)	40 W (Up to 600W With Peltier Cells)
Curve Correction to STC	IEC 80891, JRC or Anderson
Advance Fitting of I-V Curves	SEM, DEM and VDEM Models (17 Different Weight Functions)
Thermal Coefficients of Voc and Pm	Standard on All Systems (With Optional Temperature Control)
Irradiance Monitoring & Correction	Standard on All Systems

The above specifications provide general information about this product. Actual product can be customized to meet the needs of individual customers.