Rune Strandberg

• Strandberg, Rune (2023). Using transfer coefficients to model series-connected multi-junction solar cells with radiative coupling. Applied Physics Letters. ISSN 0003-6951. 122(25). doi: 10.1063/5.0152026. Full text in Research Archive Show summary

  When the quality of multi-junction solar cells becomes sufficiently high, radiative exchange of photons between cells must be included to properly model such devices. In this work, it is shown how constants called transfer coefficients can account for radiative coupling in series-connected multi-junction solar cells consisting of several sub-cells, which obey the single diode equation. The introduction of the transfer coefficients allows the relation between the voltage and current of the device to be expressed by a convenient closed-form expression that captures the general physics of radiatively coupled multi-junction cells analogous to how the single diode equation describes single-junction solar cells. Another advantage of this model is that it allows the short circuit current and open circuit voltage of radiatively coupled multi-junction cells to be easily calculated. The possibility of extending the model by including some non-idealities is briefly discussed.

• Garcia, Alfredo Sanchez; Kristensen, Sissel Tind & Strandberg, Rune (2023). The Recombination Parameter γ: Modeling and Comments. IEEE Journal of Photovoltaics. ISSN 2156-3381. 13(4), p. 516–523. doi: 10.1109/JPHOTOV.2023.3268399. Full text in Research Archive
• Garcia, Alfredo Sanchez; Kristensen, Sissel Tind & Strandberg, Rune (2022). Analytical Modeling of the Temperature Sensitivity of the Maximum Power Point of Solar Cells. IEEE Journal of Photovoltaics. ISSN 2156-3381. 12(5), p. 1237–1242. doi: 10.1109/JPHOTOV.2022.3178175. Full text in Research Archive
• Garcia, Alfredo Sanchez & Strandberg, Rune (2021). Analytical Modeling of the Maximum Power Point with Series Resistance. Applied Sciences. ISSN 2076-3417. 11(22). doi: 10.3390/app112210952. Full text in Research Archive Show summary

  This paper presents new analytical expressions for the maximum power point voltage, current, and power that have an explicit dependence on the series resistance. An explicit expression that relates the series resistance to well-known solar cell parameters was also derived. The range of the validity of the model, as well as the mathematical assumptions taken to derive it are explained and discussed. To test the accuracy of the derived model, a numerical single-diode model with solar cell parameters whose values can be found in the latest installment of the solar cell efficiency tables was used. The accuracy of the derived model was found to increase with increasing bandgap and to decrease with increasing series resistance. An experimental validation of the analytical model is provided and its practical limitations addressed. The new expressions predicted the maximum power obtainable by the studied cells with estimated errors below 0.1% compared to the numerical model, for typical values of the series resistance.

• Garcia, Alfredo Sanchez; Kristensen, Sissel Tind & Strandberg, Rune (2021). Assessment of a New Analytical Expression for the Maximum-Power Point Voltage with Series Resistance. In Angus, Rockett (Eds.), 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). IEEE conference proceedings. ISSN 978-1-6654-1922-2. p. 0961–0965. doi: 10.1109/PVSC43889.2021.9518399. Full text in Research Archive
• Kristensen, Sissel Tind; Garcia, Alfredo Sanchez; Nie, Shuai; Hameiri, Ziv & Strandberg, Rune (2020). Improved Temperature Coefficient Modeling through the Recombination Parameter γ, 2020 47th IEEE Photovoltaic Specialists Conference (PVSC) . IEEE conference proceedings. ISSN 978-1-7281-6116-7. p. 83–87. doi: 10.1109/PVSC45281.2020.9300400.
• Garcia, Alfredo Sanchez; Kristensen, Sissel Tind; Narten Christiansen, Sjur & Strandberg, Rune (2020). Temperature Coefficients of Solar Cell Parameters at Maximum Power Point, 2020 47th IEEE Photovoltaic Specialists Conference (PVSC) . IEEE conference proceedings. ISSN 978-1-7281-6116-7. p. 1232–1237. doi: 10.1109/PVSC45281.2020.9300360.
• Strandberg, Rune (2020). An Analytic Approach to the Modeling of Multijunction Solar Cells. IEEE Journal of Photovoltaics. ISSN 2156-3381. 10(6), p. 1701–1711. doi: 10.1109/JPHOTOV.2020.3013974.
• Kristensen, Sissel Tind; Nie, Shuai; Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Hameiri, Ziv (2020). Temperature Coefficients of Crystal Defects in Multicrystalline Silicon Wafers. IEEE Journal of Photovoltaics. ISSN 2156-3381. 10(2), p. 449–457. doi: 10.1109/JPHOTOV.2020.2968111.
• Garcia, Alfredo Sanchez & Strandberg, Rune (2019). Analytical Expressions for Radiative Losses in Solar Cells, 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC). IEEE conference proceedings. ISSN 978-1-7281-0494-2. doi: 10.1109/PVSC40753.2019.8980507.
• Kristensen, Sissel Tind; Nie, Shuai; Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Hameiri, Ziv (2019). How Gettering Affects the Temperature Sensitivity of the Implied Open Circuit Voltage of Multicrystalline Silicon Wafers, 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC). IEEE conference proceedings. ISSN 978-1-7281-0494-2. p. 1–7. doi: 10.1109/PVSC40753.2019.8980880.
• Strandberg, Rune (2019). A summary of expressions for central performance parameters of high efficiency solar cell concepts, 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC). IEEE conference proceedings. ISSN 978-1-7281-0494-2. doi: 10.1109/PVSC40753.2019.8981210.
• Kristensen, Sissel Tind; Nie, Shuai; Wiig, Marie Syre; Haug, Halvard; Berthod, Charly & Strandberg, Rune [Show all 7 contributors for this article] (2019). A high-accuracy calibration method for temperature dependent photoluminescence imaging. AIP Conference Proceedings. ISSN 0094-243X. 2147(1). doi: 10.1063/1.5123812. Full text in Research Archive
• Berthod, Charly; Søndergaard, Sissel Tind; Strandberg, Rune; Odden, Jan Ove; Nie, Shuai & Hameiri, Ziv [Show all 7 contributors for this article] (2019). Temperature Sensitivity of Multicrystalline Silicon Solar Cells. IEEE Journal of Photovoltaics. ISSN 2156-3381. 9(4), p. 927–964. doi: 10.1109/JPHOTOV.2019.2911871. Show summary

  This paper presents an experimental investigation of the temperature coefficients of multicrystalline silicon solar cells. The aim was to determine if some cell parameters can affect positively the temperature sensitivity without detrimental impact on the efficiency. Commercial solar cells with different bulk resistivities, compensation levels, and cell architectures have been studied. We report that the base net doping, the location of the solar cell along the brick and the cell architecture have significant impacts on the temperature coefficients. Moreover, we show how the change in recombination mechanisms along the ingot height affects the temperature coefficients. The compensation level was observed to have no significant effect on the temperature coefficients. We also demonstrate why aluminum back-surface-field and passivated emitter rear contact solar cells have similar temperature sensitivities despite a better passivation and higher open-circuit voltage for the latter cell architecture. Finally, we have found that reducing the bulk resistivity can improve the solar cells’ performance in hot climates.

• Kristensen, Sissel Tind; Odden, Jan Ove & Strandberg, Rune (2018). Temperature Dependent Suns-Voc of Multicrystalline Silicon Cells from Different Ingot Positions, Proceedings of 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7) 2018. IEEE conference proceedings. ISSN 978-1-5386-8529-7. p. 2244–2247. doi: 10.1109/pvsc.2018.8547273.
• Strandberg, Rune (2018). Analytic JV -Characteristics of Ideal Impurity PV-Cells, 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC). IEEE conference proceedings. ISSN 978-1-5090-5605-7. doi: 10.1109/PVSC.2017.8366595.
• Kristensen, Sissel Tind; Odden, Jan Ove & Strandberg, Rune (2018). Minority Carrier Lifetime Variations in Multicrystalline Silicon Wafers with Temperature and Ingot Position, 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC). IEEE conference proceedings. ISSN 978-1-5090-5605-7. p. 2651–2655. doi: 10.1109/PVSC.2017.8366683.
• Strandberg, Rune (2017). The JV-Characteristic of Intermediate Band Solar Cells With Overlapping Absorption Coefficients. IEEE Transactions on Electron Devices. ISSN 0018-9383. 64(12), p. 5027–5030. doi: 10.1109/TED.2017.2762761.
• Strandberg, Rune (2017). Analytic JV-Characteristics of Ideal Intermediate Band Solar Cells and Solar Cells With Up and Downconverters. IEEE Transactions on Electron Devices. ISSN 0018-9383. 64(5), p. 2275–2282. doi: 10.1109/TED.2017.2686359.
• Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Sætre, Tor Oskar (2016). Reduced temperature sensitivity of multicrystalline silicon solar cells with low ingot resistivity. Conference record of the Photovoltaic Specialists Conference. ISSN 0160-8371. 2016-November, p. 2398–2402. doi: 10.1109/PVSC.2016.7750071.
• Strandberg, Rune (2016). Comparison of the sensitivity to spectral variation of voltage- and current-matched tandem devices with luminescent coupling and thickness optimization. Conference record of the Photovoltaic Specialists Conference. ISSN 0160-8371. 2016-November, p. 358–363. doi: 10.1109/PVSC.2016.7749611.
• Berthod, Charly; Strandberg, Rune; Yordanov, Georgi Hristof; Beyer, Hans-Georg & Odden, Jan Ove (2016). On the variability of the temperature coefficients of mc-Si solar cells with irradiance. Energy Procedia. ISSN 1876-6102. 92, p. 2–9. doi: 10.1016/j.egypro.2016.07.002. Full text in Research Archive
• Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Sætre, Tor Oskar (2015). Reduction of temperature coefficients in multicrystalline silicon solar cells after light-induced degradation, Photovoltaic Specialist Conference (PVSC), 2015 IEEE 42nd. IEEE conference proceedings. ISSN 978-1-4799-7944-8. doi: 10.1109/PVSC.2015.7355753.
• Strandberg, Rune (2015). Spectral and temperature sensitivity of area de-coupled tandem modules, Photovoltaic Specialist Conference (PVSC), 2015 IEEE 42nd. IEEE conference proceedings. ISSN 978-1-4799-7944-8. doi: 10.1109/PVSC.2015.7356111. Full text in Research Archive
• Strandberg, Rune (2015). Heat to electricity conversion by cold carrier emissive energy harvesters. Journal of Applied Physics. ISSN 0021-8979. 118(21). doi: 10.1063/1.4936614. Full text in Research Archive
• Berthod, Charly; Strandberg, Rune & Odden, Jan Ove (2015). Temperature Coefficients of Compensated Silicon Solar Cells – Influence of Ingot Position and Blend-in-ratio. Energy Procedia. ISSN 1876-6102. 77, p. 15–20. doi: 10.1016/j.egypro.2015.07.004.
• Strandberg, Rune (2015). Theoretical efficiency limits for thermoradiative energy conversion. Journal of Applied Physics. ISSN 0021-8979. 117(5). doi: 10.1063/1.4907392.
• Strandberg, Rune (2015). Detailed balance analysis of area de-coupled double tandem photovoltaic modules. Applied Physics Letters. ISSN 0003-6951. 106(3). doi: 10.1063/1.4906602.
• Strandberg, Rune (2014). The limiting efficiency of four-band cells revisited. In King, Richard R. (Eds.), 40th IEEE Photovoltaic Specialists Conference, Proceedings of the. IEEE conference proceedings. ISSN 978-1-4799-4398-2. p. 280–284. doi: 10.1109/PVSC.2014.6924914. Show summary

  The limiting theoretical efficiency of four-band solar cells is revisited. In previous work, researchers have looked at the theoretical efficiency of four band cells where the smallest of the three sub-band gaps is closest to the valence band and the largest closest to the conduction band. In this work, limits are calculated also for other possible band configurations. In multi-band cells, photon selectivity can be assured by adjusting the band widths. The present work shows that previous authors have put too rigid constraints on the band structure to achieve spectral selectivity. Relieving these constraints gives a considerably higher limiting efficiency for cells with band width restriction than previously reported. The highest efficiency for four-band cells with band width restriction is found to be 69.4 %.

• Strandberg, Rune (2013). Evaluation of a selection of intermediate band materials based on their absorption coefficients. IEEE Journal of Photovoltaics. ISSN 2156-3381. 3(3), p. 997–1003. doi: 10.1109/JPHOTOV.2013.2261119.
• Strandberg, Rune & Reenaas, Turid Worren (2012). Initial theoretical study of solar cells with an intermediate band of non-zero width and a thermalized electron population. Progress in Photovoltaics. ISSN 1062-7995. 20(4), p. 431–441. doi: 10.1002/pip.1155. Show summary

  A model based on detailed balance principles is developed to study how the thermalized nature of the electrons in the intermediate band (IB) affects the efficiency of intermediate band solar cells. Published work on intermediate band solar cells with finite IB width has focused on the fundamental case when the absorptivity is assumed to be high for all photon energies above the smallest band gap. In this work, an attempt is made to incorporate variations in the absorptivity due to the thermal distribution of the IB electrons. In a wide IB with a thermalized electron population, there will be a low density of electrons close to the upper band edge. The density of unoccupied electron states close to the lower band edge will also be low. As a consequence, the absorption coefficients for photon energies where the only energetically allowed transitions involve exciting electrons from or to, respectively, such states can be expected to be low. The presented model incorporates the effect of the thermalized electron population in an idealized way. In some cases, the calculated efficiency is well above the limit for single band gap cells, whereas in other cases it is not. It is concluded that absorption coefficients rising rapidly from very low values to higher values are advantageous, that overlap between the absorption coefficients can be beneficial when the IB becomes sufficiently wide, and finally, that a case-by-case study probably is required to evaluate whether a particular IB material can give cells with high efficiency.

• Strandberg, Rune (2012). Theoretical efficiency of intermediate band solar cells with overlapping absorption coefficients for various combinations of band gaps. Conference record of the Photovoltaic Specialists Conference. ISSN 0160-8371. 38, p. 97–100. doi: 10.1109/PVSC.2012.6317576.
• Strandberg, Rune & Aguilera, Irene (2012). Evaluation of vanadium substituted In2S3 as a material for intermediate band solar cells. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 98, p. 88–93. doi: 10.1016/j.solmat.2011.10.008.
• Strandberg, Rune & Reenaas, Turid Worren (2011). Optimal Filling of the Intermediate Band in Idealized Intermediate-Band Solar Cells. IEEE Transactions on Electron Devices. ISSN 0018-9383. 58(8), p. 2559–2565. doi: 10.1109/TED.2011.2155659. Show summary

  The optimal filling of the intermediate band (IB) of an IB solar cell is investigated. Using models based on detailed balance principles, it is shown that the optimal filling varies with the size of the subband gaps, the absorptivity of the cell, and the degree of the overlap between the absorption coefficients as well as the mutual sizes of the absorption cross sections for transitions over the subband gaps. The results of calculations that show how nonoptimal filling affects the cell efficiency are also presented. In several cases, a deviation from the optimal filling will only result in small changes in the efficiency. However, cases where the efficiency is reduced dramatically due to nonoptimal filling are also identified. For some cases, the negative impact of nonoptimal filling can be reduced by increasing the absorptivity of the cell or, when the effect of photofilling is significant, by increasing the light concentration.

• Strandberg, Rune & Reenaas, Turid Worren (2011). Drift-diffusion model for intermediate band solar cells including photofilling effects. Progress in Photovoltaics. ISSN 1062-7995. 19(1), p. 21–32. doi: 10.1002/pip.983. Show summary

  A novel drift-diffusion model for intermediate band solar cells (IBSC) is presented. The model differs from previous drift-diffusion models by allowing the carrier concentrations in all three bands to vary. It is developed for the idealized case where only radiative recombination occurs and where the IB has zero width. The model is used to compare the performance of IBSCs where the IB-region is doped to get a partially filled IB (prefilled IBSC) to IBSCs where the IB-region is not doped to partially fill the IB (photofilled IBSC). Numerical results show that a photofilled IBSC can achieve high efficiencies when operated under concentrated light. In fact, for some particular cases, a photofilled cell will perform better than a prefilled cell. The optimal degree of prefilling, i.e. the ratio of the concentration of doping atoms to the total number of IB-states, is found for a particular example. It is also examined how the carrier concentrations in all three bands, the conduction, the intermediate and the valence bands, vary in prefilled and photofilled IBSCs. Finally, the band diagrams of a prefilled and photofilled IBSC are discussed.

• Strandberg, Rune & Reenaas, Turid Worren (2010). Limiting efficiency of intermediate band solar cells with spectrally selective reflectors. Applied Physics Letters. ISSN 0003-6951. 97(3). doi: 10.1063/1.3466269. Show summary

  So far, theoretical efficiency limits for the intermediate band solar cell have been calculated under the assumption that the absorptivity of the solar cell is 1 for all photon energies larger than the smallest subband gap. In the present work, efficiency limits have been calculated under the assumption that the cell is covered by spectrally selective reflectors. The efficiency limit for the 1 sun 6000 K black body spectrum is found to increase from 46.8% to 48.5% and the limit for the AM1.5G spectrum (as defined by ASTM G173–03) is found to increase from 49.4% to 52.0%.

• Strandberg, Rune & Reenaas, Turid Worren (2009). Photofilling of intermediate bands. Journal of Applied Physics. ISSN 0021-8979. 105(12), p. 124512-1–124512-8. doi: 10.1063/1.3153141.
• Strandberg, Rune (2008). Modelling of the electron concentration in an intermediate band. Conference record of the Photovoltaic Specialists Conference. ISSN 0160-8371. p. 1–5. doi: 10.1109/PVSC.2008.4922845.

View all works in Cristin

• Strandberg, Rune & Imenes, Anne Gerd (2023). Efficiency maps for tandem solar cells using high resolution spectral data.
• Strandberg, Rune & Imenes, Anne Gerd (2022). Production estimates for tandem cells using high resolution spectral data.
• Strandberg, Rune (2022). Solcellerelatert undervisning og forskning ved UiA.
• Tind Kristensen, Sissel; Sanchez Garcia, Alfredo; Nie, Shuai; Hameiri, Ziv & Strandberg, Rune (2020). Improved Temperature Coefficient Modeling through the Recombination Parameter γ.
• Garcia, Alfredo Sanchez & Strandberg, Rune (2019). Analytical Expressions for Radiative Losses in Solar Cells.
• Kristensen, Sissel Tind; Nie, Shuai; Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Hameiri, Ziv (2019). How Crystal Defects Affect the Thermal Behavior of the Open Circuit Voltage of Multicrystalline Silicon Solar Cells.
• Kristensen, Sissel Tind; Nie, Shuai; Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Hameiri, Ziv (2019). How Gettering Affects the Temperature Coefficient of the Voc of Multicrystalline Silicon Solar Cells.
• Søndergaard, Sissel Tind; Odden, Jan Ove & Strandberg, Rune (2018). Temperature dependent suns-Voc of mc-Si cells from different ingot positions.
• Strandberg, Rune (2017). Analytic JV-Characteristics of Ideal Impurity PV-Cells.
• Søndergaard, Sissel Tind; Strandberg, Rune & Odden, Jan Ove (2017). Minority Carrier Lifetime Variations in Multicrystalline Silicon Wafers with Temperature and Ingot Position.
• Strandberg, Rune (2017). Fotoner - hvordan høste dem mest mulig effektivt?
• Strandberg, Rune (2017). The JV-characteristics of high-efficiency PV-concepts.
• Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Sætre, Tor Oskar (2016). Reduced Temperature Sensitivity of Multicrystalline Silicon Solar Cells with Low Ingot Resistivity.
• Strandberg, Rune (2016). Comparison of the Sensitivity to Spectral Variation of Voltage- and Current-Matched Tandem Devices with Luminescent Coupling and Thickness Optimization.
• Berthod, Charly; Strandberg, Rune; Yordanov, Georgi Hristof; Beyer, Hans-Georg & Odden, Jan Ove (2016). On the Variability of the Temperature Coefficients of mc-Si Solar Cells with Irradiance.
• Strandberg, Rune (2016). Solceller.
• Berthod, Charly; Strandberg, Rune & Odden, Jan Ove (2015). Temperature Coefficients of Compensated Silicon Solar Cells – Influence of Ingot Position and Blend-in-ratio.
• Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Sætre, Tor Oskar (2015). Reduction of Temperature Coefficients in Multicrystalline Silicon Solar Cells after Light-Induced Degradation.
• Strandberg, Rune (2015). Emitterende energihøstere.
• Strandberg, Rune (2015). Spectral and Temperature Sensitivity of Area De-Coupled Tandem Modules.
• Strandberg, Rune (2015). Arealdekoblede tandemmoduler.
• Strandberg, Rune (2015). Solcellekonsepter med høy virkningsgrad.
• Skomedal, Gunstein & Strandberg, Rune (2015). Framtida møtes best forlengs. Fædrelandsvennen. ISSN 0805-3790.
• Strandberg, Rune (2015). Measurement of minority carrier lifetime at elevated temperature. Show summary

  Foredrag på workshop med deltakere fra Elkem Solar, UiA, Teknova, IFE, Høyskolen i Vestfold og EPFL (Neuchatel, Sveits).

• Strandberg, Rune (2015). Area de-coupled tandem modules.
• Strandberg, Rune (2014). Fornybar energi.
• Strandberg, Rune (2013). Production data from 45 kWp solar power plant in Kristiansand.
• Eikeland, Torgeir; Imenes, Anne Gerd & Strandberg, Rune (2010). Solcelleparker kan erstatte vannkraft. [Newspaper]. Fedrelandsvennen. Show summary

  Kommentar: Tittelen er feilsitert.

• Strandberg, Rune & Reenaas, Turid Worren (2009). Photofilling of Intermediate Bands.
• Strandberg, Rune & Reenaas, Turid Worren (2008). Investigation of an alternative intermediate band solar cell design.
• Strandberg, Rune & Reenaas, Turid Worren (2008). Modelling of the Electron Concentration in an Intermediate Band.
• Strandberg, Rune (2008). Intermediate Band Solar Cells.
• Thomassen, Sedsel Fretheim; Reenaas, Turid Worren; Strandberg, Rune; Hunderi, Ola; Fimland, Bjørn-Ove & Sadeghi, Mahdad [Show all 7 contributors for this article] (2007). Growth of quantum dots for intermediate band solar cells.
• Thomassen, Sedsel Fretheim; Worren, Turid; Fimland, Bjørn-Ove; Strandberg, Rune & Myrvågnes, Geir (2006). Quantum Dot Intermediate Band Solar Cells.
• Strandberg, Rune & Worren, Turid (2006). PC1D-simulations of solar cells containing regions with enhanced infrared absorption.
• Strandberg, Rune; Thomassen, Sedsel Fretheim & Worren, Turid (2006). Quantum dot intermediate band solar cells.
• Garcia, Alfredo Sanchez & Strandberg, Rune (2022). Theoretical Studies in Solar Cell Physics. Universitetet i Agder. ISSN 978-82-8427-103-3. Full text in Research Archive
• Skaaland, Åsbjørn; Ricke, Michael; Wallevik, Kristin; Strandberg, Rune & Imenes, Anne Gerd (2011). Potential and Challenges for Building Integrated Photovoltaics in the Agder Region. Agderforskning.

View all works in Cristin