Spectrally tuned solar cells for improved energy harvesting

The PV Tune project is an applied research project funded by the Cyprus Research Promotion Foundation. The project consortium is developing a methodology to help photovoltaic cell manufacturers optimise their designs by predicting how the spectral response of cells affects their annual energy yield.

What's it about?

The transition from finite, fossil-fuel based energy sources to clean, renewable energy sources is one of the great technical challenges facing mankind today.

The sun is an abundant, renewable and widely-distributed energy source that could easily provide all the energy required by our modern lifestyles.

Photovoltaic power stations convert sunlight directly into electricity, and are now a well-established renewable energy technology providing clean, affordable energy to millions of people across the world.

At the University of Cyprus we are studying the electricity generation potential for the next generation of photovoltaic technologies that are even more efficient than today's systems.

These next-generation devices work by using a greater proportion of sunlight reaching them, resulting in an overall increase in energy conversion efficiencies.

A new approach to designing advanced solar cells means they can be optimised for the sky conditions at a given location, potentially resulting in even higher energy yields.

PV-TUNE is a project that aims to quantify the potential for increasing solar energy yields through optimisation of photovoltaic cell designs. The project is a collaboration between a group of leading institutions in the field of high-concentration photovoltaics with the goal of collecting real outdoor data to support the theoretical gains in performance suggested by models.

The PV-TUNE project started in June 2013, and is scheduled to run for 24 months.

Project Overview

Scientific Objectives

  • Generation of a spectral resource dataset for a 'Typical Meteorological Year' in Cyprus.

A key aspect of evaluating the potential for a new cell design is to know the spectral irradiance resource at the location in which it will be used. For this reason, a dataset will be prepared that will be representative of the spectral resource of a 'Typical Meteorological Year' in Nicosia, Cyprus. This will be prepared using the SMARTS atmospheric model and validated using real on-site measurements.

  • Creation and validation of an energy production model for triple-junction cells under real operating conditions.

Given the spectral irradiance resource of an installation site, in combination with other environmental parameters, a model will be prepared to simulate the output of a module incorporating multi-junction photovoltaic cells. This model will include all the known phenomena occurring within the cell including coupling effects between cells, and will be used to evaluate the suitability of a particular cell design for a given location.

  • Development of standardised practices for multi-junction PV cell measurement.

To understand the performance of multi-junction cells under real operating conditions, a comprehensive set of characterisation procedures are required. These are to be performed indoors under controlled conditions, and cells are to be exposed to different temperatures and irradiance conditions. This work will support efforts to develop international standards for the characterisation procedures of multi-junction cells, as well as feed information directly into the models being developed within the PV-TUNE project.

  • Identification and quantification of measurement uncertainties in outdoor module energy rating.

At present, the IEC technical committee 82, working group 7 is developing international standards for the energy rating procedures for concentrator photovoltaic modules. These standards are still at an early stage of development, and the work being performed within the scope of the PV-TUNE project will feed directly into developing better understanding of the uncertainties and challenges of assigning energy ratings to this technology.

  • Identification and quantification of measurement uncertainties in indoor multi-junction cell characterisation.

The understanding of the performance of CPV modules under outdoor conditions relies on a detailed understanding of the performance characteristics of the cells within the modules under a range of different operating conditions. Therefore the PV-TUNE project will involve a detailed assessment of the indoor cell test procedure uncertainties in order to improve the confidence in outdoor measurements and to correct observations to standard reporting conditions.

Technical Objectives

  • The acquisition of a comprehensive environmental dataset with low measurement uncertainty.

One of the cornerstones of the analyses to be performed within the scope of the PV-TUNE project is a high-quality set of environmental parameters measured regularly, with minimal disturbances, and to a traceable level of uncertainty. For this reason, great care has been taken to prepare a high-quality meteorological measurement station, which includes:

  • Wind speed and direction
  • Ambient Temperature
  • Direct Normal and Global Normal broadband solar irradiance
  • Air pressure and humidity levels
  • Spectral irradiance measurements over the range 300−1700 nm

All these parameters are recorded at 5 minute intervals, and traceable to international reference centres where possible.

  • Creation of a high-quality infrastructure for spectrally-resolved measurement of the solar irradiation.

Due to the high costs of the required equipment, there are few locations across the world where high-resolution measurements of the direct normal solar spectrum is being recorded. Furthermore, the effort to maintain a reliable measurement infrastructure over extended periods of time make it harder to find high-quality spectrally-resolved DNI measurements. One outcome of the PV-TUNE project will be just such a dataset that will be made available for analysis and use in validation of models.

  • Fabrication of a set of robust, high-efficiency concentrator photovoltaic (CPV) modules for continuous long-term outdoor operation.

To investigate the effect of spectral response on energy yield over the period of a year, two sets of small CPV modules will be fabricated that will each contain a different type of photovoltaic cells with a correspondingly different spectral response. To determine the difference in output due to the cell design, the modules will be fabricated in an identical way and continually monitored side-by-side outdoors under real operating conditions. A year of data will be collected alongside the environmental dataset described above, and this will be used to extract information that will indicate how the spectral response of the cells affects the final energy yield of each cell design.

  • Development of an advanced characterisation set-up for multi-junction cell measurement.

To perform the advanced measurements required for a detailed understanding of the cell performance under real operating conditions, a state-of-the-art infrastructure will be assembled for indoor characterisation of multi-junction cells. The set-up will allow the measurement of device spectral response, spectrally-resolved electroluminescence, photoluminescence, temperature coefficients over the anticipated outdoor operating ranges as well as allowing the study of advanced intra-junction effects such as luminescent coupling.

  • Round-robin measurement campaign of MJ cells and CPV modules.

In order to lower the inherent measurement uncertainties and to improve confidence levels in the measurements being taken on site, a number of leading institutions in the field of CPV module and cell measurement will be involved in the evaluation of the module performances at different sites. The comparison of current-voltage characteristics will provide valuable information on the quality of the monitoring infrastructures involved.

  • Modelling and validation of the spectrally-resolved solar resource in Nicosia, Cyprus using the SMARTS atmospheric modelling tool.

The information gained through the environmental monitoring campaign will be fed into the SMARTS atmospheric model to produce a year's dataset of 5-minute direct normal spectral irradiance values. The data will be filtered to remove occasions where the irradiance levels are too low to significantly contribute to the yield of CPV systems, and thereby deal with clear-sky conditions that are suitable for electricity generation. The results will be validated against the measured spectral conditions corresponding to the on-site environmental conditions, and the model refined until the closest possible agreement is obtained. Finally, a 'Typical Meteorological Year' dataset will be fed into the model to arrive at a corresponding 'Typical Annual Spectra Resource'.

Project Partners

UCY logo

Project Coordinator:
University of Cyprus, Photovoltaic Technology [UCY]

UCY logo

University of Stuttgart, Institute for Photovoltaics [IPV]

UCY logo

Cyprus Energy Regulatory Authority [CERA]

The PV-TUNE project is co-financed by the European Regional Development Fund and the Republic of Cyprus through the Research Promotion Foundation (Cyprus) in the framework of the project ‘Spectrally Tuned Solar Cells for Improved Energy Harvesting’ with grant number ΤΕΧΝΟΛΟΓΙΑ/ΕΝΕΡΓ/0311(ΒΙΕ)/13.

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Latest Results


  • Calibration of spectroradiometers for outdoor direct solar spectral irradiance measurements
Paraskeva Vasiliki, Matthew Norton, Maria Hadjipanayi, George E. Georghiou
Proceedings of the 28th European Photovoltaic and Solar Energy Conference and Exhibition, Paris, France, September 2013, WIP Munich.
pdfDownload paper
  • Photoluminescence analysis of coupling effects: The impact of shunt resistance and temperature
V.Paraskeva, C.Lazarou, M.Hadjipanayi, M.Norton, M. Pravettoni, G.E.Georghiou, M.Heilmann, S.Christiansen
Sol. Energy Mater. Sol. Cells vol. 130, pp. 170–181, 2014
pdfDownload paper
  • Luminescent emission of multi-junction InGaP/InGaAs/Ge PV cells under high intensity irradiation
V.Paraskeva, M.Norton, M.Hadjipanayi, M. Pravettoni, G.E.Georghiou
Sol. Energy Mater. Sol. Cells vol. 134, pp. 175–184, 2015
pdfDownload paper
  • The effect of shunt resistance on External Quantum Efficiency measurements at high light bias conditions
V.Paraskeva, M.Hadjipanayi, M.Norton, M.Pravettoni, G.E.Georghiou
Proc. 40th IEEE Photovoltaic Specialist Conference (2014) pp.3664-3669
pdfDownload paper
  • High quality Measurements of the Solar Spectrum for Simulation of Multi-Junction Photovoltaic Cell Yields
M.Norton, V.Paraskeva, R.Galleano, G.Makrides, R.Kenny, G.E.Georghiou
Proc.29th EUPVSEC (2014) pp.2002-2007
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  • Theory and numerical simulation of the physical processes involved in the potential induced degradation of conventional silicon solar cells
N. Kindyni, C. Lazarou, George E. Georghiou
Proc. 40th IEEE Photovoltaic Specialist Conference (2014)
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  • Field investigation of the Effect of Spectral Response upon Photovoltaic Energy yields
M.Norton, V.Paraskeva, R.Kenny, G.E.Georghiou
Proc. 42nd IEEE Photovoltaic Specialist Conference (2015)(Preprint)
pdfDownload paper


If you wish to have further information on the work carried out in this project, or are interested in possible collaboration, please feel free to email us at the following address:
Dr Matthew Norton

Our site is located at the University of Cyprus' Photovoltaic Technology Park, in Nicosia Cyprus. The coordinates of this location are:‎
35.147705, 33.416977‎
+35° 8' 51.74", +33° 25' 1.12"
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