Second international spectroradiometer intercomparison: preliminary results and impact on PV device calibration

This paper describes the preliminary results of an intercomparison of spectroradiometers for global (GNI) and direct normal incidence (DNI) irradiance in the visible (VIS) and near infrared (NIR) spectral regions together with an assessment of the impact these results may have on the calibration of triple-junction photovoltaic devices and on the relevant spectral mismatch calculation. The intercomparison was conducted by six European scientific laboratories and a Japanese industrial partner. Seven institutions and seven spectroradiometer systems, representing different technologies and manufacturers were involved, representing a good cross section of the todays available instrumentation for solar spectrum measurements

Second international spectroradiometer intercomparison: results and impact on PV device calibration

This paper describes the results of an intercomparison of spectroradiometers for measuring global normal incidence and direct normal incidence spectral irradiance in the visible and in the near infrared, together with an assessment of the impact these results may have on the calibration of the short circuit current (I-sc) of triple-junction photovoltaic devices and on the relevant spectral mismatch calculation. The intercomparison was conducted by six European scientific laboratories and a Japanese industrial partner. Seven spectroradiometer systems, for a total of 13 different instruments/channels using two different technologies and made by four different manufacturers were involved. This group of systems represents a good cross section of the instrumentation for solar spectrum measurements available to date. The instruments were calibrated by each partner prior to the intercomparison following their usual procedure and traceability route in order to verify the entire measurement and traceability chain. The difference in measured spectral irradiance showed to have an impact on the calibration of a set of Iso-Type cells varying from +/- 2% to +/- 14% for middle and bottom cell, respectively

Optical modelling based on angle and temperature dependent EQE measurements on III-V multi-junction solar cells

International audienc

Capabilities of Grazing Incidence X-ray Diffraction in the Investigation of Amorphous Mixed Oxides with Variable Composition

X-ray Diffraction has been fully exploited as a probe to investigate crystalline materials. However, very little research has been carried out to unveil its potentialities towards amorphous materials. In this work, we demonstrated the capabilities of Grazing Incidence X-ray Diffraction (GIXRD) as a simple and fast tool to obtain quantitative information about the composition of amorphous mixed oxides. In particular, we evidenced that low angle scattering features, associated with local structure parameters, show a significant trend as a function of the oxide composition. This evolution can be quantified by interpolating GIXRD data with a linear combination of basic analytical functions, making it possible to build up GIXRD peak-sample composition calibration curves. As a case study, the present method was demonstrated on Ta2O5–SiO2 amorphous films deposited by RF-magnetron sputtering. GIXRD results were validated by independent measurement of the oxide composition using Rutherford Backscattering Spectrometry (RBS). These materials are attracting interest in different industrial sectors and, in particular, in photovoltaics as anti-reflection coatings. Eventually, the optical properties measured by spectroscopic ellipsometry were correlated to the chemical composition of the film. The obtained results highlighted not only a correlation between diffraction features and the composition of amorphous films but also revealed a simple and fast strategy to characterize amorphous thin oxides of industrial interest

Study of the Cross-Influence between III-V and IV Elements Deposited in the Same MOVPE Growth Chamber

We have deposited Ge, SiGe, SiGeSn, AlAs, GaAs, InGaP and InGaAs based structures in the same metalorganic vapor phase epitaxy (MOVPE) growth chamber, in order to study the effect of the cross influence between groups IV and III-V elements on the growth rate, background doping and morphology. It is shown that by adopting an innovative design of the MOVPE growth chamber and proper growth condition, the IV elements growth rate penalization due to As “carry over” can be eliminated and the background doping level in both IV and III-V semiconductors can be drastically reduced. In the temperature range 748–888 K, Ge and SiGe morphologies do not degrade when the semiconductors are grown in a III-V-contaminated MOVPE growth chamber. Critical morphology aspects have been identified for SiGeSn and III-Vs, when the MOVPE deposition takes place, respectively, in a As or Sn-contaminated MOVPE growth chamber. III-Vs morphologies are influenced by substrate type and orientation. The results are promising in view of the monolithic integration of group-IV with III-V compounds in multi-junction solar cells

Second international spectroradiometer intercomparison: results and impact on PV device calibration

This paper describes the results of an intercomparison of spectroradiometers for measuring global (GNI) and direct (DNI) normal incidence spectral irradiance in the visible (VIS) and in the near infrared (NIR), together with an assessment of the impact these results may have on the calibration of the short circuit current (Isc) of triple-junction photovoltaic devices and on the relevant spectral mismatch calculation. The intercomparison was conducted by six European scientific laboratories and a Japanese industrial partner. Seven institutions and seven spectroradiometer systems, for a total of thirteen different instruments/channels using two different technologies and made by four different manufacturers were involved. This group of systems represents a good cross section of the instrumentation for solar spectrum measurements available to date. The instruments were calibrated by each partner prior the intercomparison following their usual procedure and traceability route in order to verify the entire measurement and traceability chain. The difference of measured spectra shape showed to have an impact on the calibration of a set of Iso-Type cells varying from ±2% to ±12% for middle and bottom cell, respectively.JRC.F.7-Renewables and Energy Efficienc

Spectroradiometry in PV: how inter-laboratory comparison may improve measurement accuracy

Spectroradiometry is a key metrological discipline for accurate testing of photovoltaic (PV) devices, particularly relevant both for indoor testing on solar simulators and for outdoor testing, where differences between the available thermal energy and the energy usable by PV modules are relevant. In fact, as to indoor testing, the uncertainty in the spectral mismatch between the testing light source and the reference spectral irradiance may give rise to deviations up to 1-3% when measuring the maximum power even on a Class A solar simulator. Experimental uncertainty is expected to increase even further after the publication of the new revision of IEC 60904-9 (“Solar simulator performance requirements”), which is due by 2018. As to outdoor testing, accurate knowledge of solar spectral irradiance is important also for energy rating purposes, in view of the publication of IEC 61853 part 3 (“Energy rating of PV modules”) and part 4 (“Standard reference climatic profiles”). The relevance of accurate measurements of solar spectral irradiance has led the most renowned accredited European solar PV test centres to take part to a series of International Spetroradiometer Intercomparisons that has taken place every year so far since 2011 in various localities in the Mediterranean Basin. The ever-growing number of participating laboratories is both a consequence and a key of success of the whole exercise: ISO 17025 accredited laboratories are willing to receive confirmation of the stability and accuracy of their spectroradiometers and that can be done only when a conspicuous number of testing centres is involved. This paper summarizes the outcomes of the last intercomparisons, trying to highlight whether improvements in measurement reproducibility can be inferred from those partners that have participated since the earliest editions. The work gives new insights into spectroradiometry for both outdoor and indoor testing applications.JRC.C.2-Energy Efficiency and Renewable