Photovoltaic Efficiency Measurements Keith Emery National Renewable Energy Lab 1617 Cole Blvd. Golden,CO 80401 Email:[email protected]Cells: Coordinator: Tom Moriarty Charles Mack Modules: Coordinator: Steve Rummel Allen Anderberg Laurence Ottoson Concentrator Cells : James Kiehl
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Modules: Coordinator: Steve RummelAllen AnderbergLaurence Ottoson
Concentrator Cells : James Kiehl
NCPV
M&C Mgmt/Main.ContractsP. Sheldon
AnalyticalMicroscopy Task
M. Al-Jassim
Cell & ModulePerformance Task
K. Emery
Surface AnalysisTask
S. Asher
Electro-OpticalCharact. Task
R. Ahrenkiel
ProcessIntegration Task
B. Nelson
HiPer PV Task
Measurements Division
Support:Providing routine and specialized measurement and characterization support for research and industry teams in the photovoltaics program. Meet customer needs through rapid and direct response to requests;
Collaborative R&D:Contributing to and leading collaborative research projects to address critical issues and problems in key PV technology areas;
Technique and Diagnostic Development:Developing and implementing new and specialized measurement techniques that enhance the ability to understand and advance fundamental photovoltaic R&D. Devising diagnostic tools to advance manufacturing research and development.
Division mission
Goal - Flat Plate cell & modules
Determine Current versus Voltage under Continuous IlluminationAt 25 °C Junction Temperature
1000 W/m2 Total IrradianceASTM or IEC Global Reference
Spectrum
Goal - Concentrator Cells
Determine Current versus Voltage under Continuous IlluminationAt 25 °C Junction Temperature
1000 W/m2 Total IrradianceASTM G173 DirectReference Spectrum
Goal - Air Mass 0 / Extraterrestrial Cells
Determine Current versus Voltage under Continuous Illumination
At 25 °Cand 1 AU from the sun
Reference Spectra
IV Theory
ITest, Ref =I Test,SourceI Ref,Ref
I Ref,SourceM
M =
ERef λ( )SRef λ( )dλλ1
λ2
∫
ERef λ( )STest λ( )dλλ1
λ 2
∫
ESource λ( )STest λ( )dλλ1
λ2
∫
ESource λ( )SRef λ( )dλλ1
λ2
∫
Source of DifferencesProcedural
Calibration lab - formalInternal researchers - variableManufacturers - marketing, Power MarkExternal can not distinguish between calibration lab and internal
Definition Area - total, active, aperture, typical, not measured
Data Acquisition SystemVoltage bias rate - too fast for pulsed systemsVoltage bias direction - rarely both directions
so hysteresis can not be detectedPre-measurement conditions
voltage (0V,0A or Pmax), light, temperature, humidity
HP34401 DMMVoltage
PVdevice
HP434401 DMMCurrent
Kepco 50V,16ALoad
Ri
Light source Size/Temperature Voltage Currentlimits limits
0.1 - 20 suns 30 cm x 30 cm ±0.5 mV ±10 pAfiltered 3 kW Xe 5-50 °C ±50 V ±16 A
1-sun Cells & Modules
SpireSize / Voltage Current
Temperature limits limits61 x 122 cm 0.1 mV 0.5 mA25 °C (20-50 °C) 100 V 20 A0.1 to 1.2 suns
LACSSSize Voltage Current
limits limits152 cm x 122 cm ±0.5 mV ±1 µAfiltered 25 kW Xe ±300 V ±60 A0.1 to 20 suns
Outdoor 1-sun test bedSize Voltage Current
limits limits200 x 300 cm ±0.5 mV ±1 µA2-axis positioning ±300V ±60 A
Vacuum stage with thermoelectrictemperature control (5-80°C)
Current tovoltageconverter
PV Sample
Biaslight
ReferenceDetector
IEEE-488
Stanford 810Lock-in Amp.
Semiconductoror Pyroelectric
LensGimbalmountedmirror
control lines
Digital I/O
Computer to Control,Store,
Analyze, Plot,and Report
real-timecalibration
Apparatus to measure the QE of a givencell in a thin-film module
bias lightmonochromaticlight from filtersystem
bias light
aperture toilluminate 1 cell Series connected module
mask to block bias lightto cell being measured- +
Module / Multi-Junction Responsivity
Concentrator CellsI-V Applications
Test bed Light source Voltage Currentsize/temperature limits limits
Continuous 1 kW Xe or ~ 1cm diameter ±0.1 mV ±1 µA Concentrator 7 kW tungsten for Xe, 5 x 10 cm ±10V ±10 A
1 to 200 suns for IR lamp, 5-80 °C
Spectrolab HIPSS 1 ms Xe flash 2 cm x 20 cm 0.1 mV 500 µA1 to 2000 suns 100 V 50 A
PVUSA style regression for rapid analysis (<1min) of field data
Light trapA mono-crystalline solar cell's efficiency improves when encapsulated because the encapsulation utilizes a white border providing additional light to the cell via internal reflections.
Asymptotically approachingsteady state Voc at elevated
temperature
1 ms shutter opened with thedevice at a known temperature
Isc TEMP
0
10
20
30
40
50
1900 2000 2100 2200Wavelength (nm)
25°C
35°C
45°C
55°C
69°C
Bias rate, direction
Temperature Coefficient
Light trap
A mono-crystalline solar cell's efficiency improves when encapsulated because the encapsulation utilizes a white border providing additional light to the cell via internal reflections.