Rune Strandberg

• Strandberg, Rune (2026). Non-optimal yet useful bandgap combinations for multijunction solar cells. Journal of Applied Physics. ISSN 0021-8979. 140(4). doi: 10.1063/5.0340335. Full text in Research Archive Show summary

  The optimal bandgap combinations for multijunction solar cells are well known. The bandgaps used in practical devices may deviate from these optimal values depending on the availability of suitable materials. This work explores the non-ideal but still useful bandgap combinations that exist for multijunction cells with up to six subcells. It is found that principal component analysis can be utilized to establish rules of thumb for how the bandgaps in multijunction devices should be collectively adjusted to maintain high efficiency. This realization allows bandgap configurations with high theoretical efficiency to be identified with a few easy calculations, as demonstrated by a practical example.

• Strandberg, Rune & Imenes, Anne Gerd (2024). Bandgap Optimization of Photovoltaic Tandem Cells Based on Spectra Collected over a Full Year. Solar RRL. p. 1–16. doi: 10.1002/solr.202400490. Full text in Research Archive Show summary

  Spectral data collected every minute at the test station in Grimstad, Norway, are used to investigate the impact of spectral variation on tandem cells. The results are displayed as efficiency maps which are compared to equivalent maps for the air mass 1.5 global (AM1.5G) reference spectrum. Most of the maps are calculated for ideal cells and will thus serve as benchmarks for what can possibly be achieved under real conditions, but the impact of non-radiative recombination is also included. It is found that there is generally good agreement between the efficiency under the AM1.5G spectrum and the efficiency found using the collected spectra. The main difference is that a slight blueshift in the real spectra favors larger bandgaps. Seasonal efficiency maps and maps for different types of conditions are also presented. The largest deviation from the reference spectrum is found for the three darkest months of the year. Optimizing the bandgaps for this period may increase seasonal production by several percent, albeit with a significant accompanying reduction in annual production. For June, the sunniest month, as well as for cloudy and lowlight conditions, it is found that the optimal bandgaps are slightly larger than those found for the AM1.5G.

• 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 Show summary

  The recombination parameter γ appears in mathematical expressions for the temperature coefficient of solar cells. This work presents a new analytical expression for this parameter. The expression is derived assuming that all nonradiative recombination occurs in the neutral region of the cell, where carrier diffusion is the dominant transport mechanism. The model shows a direct relation between γ and the temperature sensitivities of the carrier mobility and lifetime. Problems concerning the original definition of γ and its temperature and voltage dependence are discussed and, when possible, amended. A further investigation of the possibility of defect characterization through γ is presented. This yields two analytical expressions that link γ to defect characteristics. A numerical evaluation of the derived expressions is performed for a number of impurities. It is concluded that the recombination parameter γ alone may not be suitable for defect characterization.

• 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 Show summary

  Abstract—This article presents new analytical expressions for the temperature coefficients of the voltage, current, and power of a solar cell at its maximum power point MPP). A new analytical expression of the temperature coefficient of the fill factor is also derived. The new expressions are written as functions of photovoltaic (PV) metrics that can be obtained from i-V measurements. Nonideal diode behavior is partially accounted for through a temperature dependent ideality factor. The recombination parameter γ, which has been shown to account for the thermal sensitivity of all mechanisms determining the open-circuit voltage, appears to play a role also for the temperature coefficient of theMPP. The expressions are tested against experimental data, which covers measurements from 18 multicrystalline silicon solar cells with different bulk resistivities and cell architectures. It is found that the new model captures the essence of the temperature variation shown by the investigated PV metrics.

• 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 (Institute of Electrical and Electronics Engineers). ISSN 9781665419222. p. 0961–0965. doi: 10.1109/PVSC43889.2021.9518399. Full text in Research Archive Show summary

  This work compares a recently developed analytical expression for the maximumpower point voltage with experimental data, to test its usability for crystalline silicon solar cells. The experimental data covers measurements from 18 multicrystalline silicon solar cells with different bulk resistivities and cell architectures. We show that the expression is able to predict the maximum power obtainable by the measured cells with relative discrepancies below 1%. Additionally, we compare the accuracy of this new expression with two already existing models.

• Garcia, Alfredo Sanchez & Strandberg, Rune (2021). Analytical Modeling of the Maximum Power Point with Series Resistance. Applied Sciences. 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.

• 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 (Institute of Electrical and Electronics Engineers). ISSN 9781728161167. p. 83–87. doi: 10.1109/PVSC45281.2020.9300400. Full text in Research Archive
• Garcia, Alfredo Sanchez; Kristensen, Sissel Tind; Christiansen, Sjur Narten & Strandberg, Rune (2020). Temperature Coefficients of Solar Cell Parameters at Maximum Power Point, 2020 47th IEEE Photovoltaic Specialists Conference (PVSC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781728161167. p. 1232–1237. doi: 10.1109/PVSC45281.2020.9300360. Full text in Research Archive Show summary

  Analytical expressions for the temperature coefficients of the maximum power point voltage and current are presented. The temperature coefficients are calculated assuming the bandgap to be a linear function of the temperature and accounting for energy losses of non-radiative nature. The latter are introduced in the model through the External Radiative Efficiency. The so-called γ parameter, which has been shown to account for the thermal sensitivity of all mechanisms determining the open-circuit voltage, appears to also play a role in the temperature coefficient of the maximum power point voltage and current. Numerical results and a comparison with experimental measurements are also presented.

• 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. Full text in Research Archive Show summary

  This article investigates the influence of crystallographic defects on the temperature sensitivity of multicrystalline silicon wafers. The thermal characteristics of the implied open-circuit voltage is assessed since it determines most of the total temperature sensitivity of the material. Spatially resolved temperature-dependent analysis is performed on wafers from various brick positions; intragrain regions, grain boundaries, and dislocation clusters are examined. The crystal regions are studied before and after subjecting the wafers to phosphorus gettering, aiming to alter the metallic impurity concentration in various regions across the wafers. Most intragrain regions and grain boundaries are found to show similar thermal characteristics before gettering. The gettering process has no substantial effect on the temperature sensitivity of intragrain regions, whereas it increases the sensitivity of most grain boundaries. Dislocation clusters exhibit both highest and lowest temperature sensitivities compared with other crystal regions before and after gettering. Images of the recombination parametery are created and related to the temperature sensitivity of the Shockley-Read-Hall (SRH) lifetime of the impurities in the material. The results suggest that most intragrain regions and grain boundaries are limited by SRH centers with a modest lifetime temperature sensitivity in the studied temperature range. Dislocation clusters are found to contain recombination centers with an effective lifetime that has a beneficial temperature sensitivity. The gettering process is observed to alter the composition of the recombination centers in the dislocation clusters, resulting in an SRH lifetime with an even more favorable temperature sensitivity for most clusters.

• 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. Full text in Research Archive
• 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 (Institute of Electrical and Electronics Engineers). ISSN 9781728104942. doi: 10.1109/PVSC40753.2019.8981210. 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. Full text in Research Archive 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.

• Garcia, Alfredo Sanchez & Strandberg, Rune (2019). Analytical Expressions for Radiative Losses in Solar Cells, 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781728104942. doi: 10.1109/PVSC40753.2019.8980507. Full text in Research Archive
• 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 (Institute of Electrical and Electronics Engineers). ISSN 9781728104942. p. 1–7. doi: 10.1109/PVSC40753.2019.8980880. Full text in Research Archive
• 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
• Strandberg, Rune (2018). Analytic JV -Characteristics of Ideal Impurity PV-Cells, 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781509056057. doi: 10.1109/PVSC.2017.8366595. Full text in Research Archive
• 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 (Institute of Electrical and Electronics Engineers). ISSN 9781538685297. p. 2244–2247. doi: 10.1109/pvsc.2018.8547273. Full text in Research Archive
• 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 (Institute of Electrical and Electronics Engineers). ISSN 9781509056057. p. 2651–2655. doi: 10.1109/PVSC.2017.8366683. Full text in Research Archive
• 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. Full text in Research Archive
• 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. Full text in Research Archive
• 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. Full text in Research Archive
• 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. Full text in Research Archive
• 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. 92, p. 2–9. doi: 10.1016/j.egypro.2016.07.002. Full text in Research Archive
• Strandberg, Rune (2015). Spectral and temperature sensitivity of area de-coupled tandem modules, Photovoltaic Specialist Conference (PVSC), 2015 IEEE 42nd. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781479979448. doi: 10.1109/PVSC.2015.7356111. Full text in Research Archive Show summary

  Area de-coupling is a recently suggested method for current- or voltage-matching two-terminal tandem modules. It has previously been shown that under standard conditions, area de-coupled modules have the same theoretical efficiency as four-terminal tandem cells for any combinations of band gaps. In this work, the spectral and temperature sensitivity of ideal area de-coupled modules is investigated by detailed balance modeling. Voltage-matched area de-coupled modules are found to be considerably less sensitive to changes in the spectrum than current-matched modules. Current-matched modules are, on the other hand, found to be less sensitive to changes in the temperature. Under normal conditions, the difference in temperature sensitivity has a negligible impact on the efficiency compared to the difference in spectral sensitivity, making voltage-matched modules the preferred choice. The difference in efficiency between an area de-coupled voltage-matched module and a four-terminal device is found to be too small to be of any practical consequence even under changing conditions. This finding is in agreement with earlier work by Lentine et al. on microsystem-enabled photovoltaic modules. g

• 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. 77, p. 15–20. doi: 10.1016/j.egypro.2015.07.004. 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 (Institute of Electrical and Electronics Engineers). ISSN 9781479979448. doi: 10.1109/PVSC.2015.7355753. 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
• Strandberg, Rune (2015). Theoretical efficiency limits for thermoradiative energy conversion. Journal of Applied Physics. ISSN 0021-8979. 117(5). doi: 10.1063/1.4907392. Full text in Research Archive
• 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. Full text in Research Archive
• 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 (Institute of Electrical and Electronics Engineers). ISSN 9781479943982. p. 280–284. doi: 10.1109/PVSC.2014.6924914. Full text in Research Archive 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. Full text in Research Archive
• 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. Full text in Research Archive 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. Full text in Research Archive
• 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. Full text in Research Archive
• 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. Full text in Research Archive 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 (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. Full text in Research Archive 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 (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. Full text in Research Archive 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. Full text in Research Archive
• 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. Full text in Research Archive

View all works in NVA

• Strandberg, Rune (2025). Band gap optimization of multijunction cells with up to six subcells. Full text in Research Archive
• Strandberg, Rune & Imenes, Anne Gerd (2023). Efficiency maps for tandem solar cells using high resolution spectral data. Full text in Research Archive
• Strandberg, Rune (2022). Solcellerelatert undervisning og forskning ved UiA. Full text in Research Archive
• Strandberg, Rune & Imenes, Anne Gerd (2022). Production estimates for tandem cells using high resolution spectral data. 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. Full text in Research Archive
• 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. Full text in Research Archive
• 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. Full text in Research Archive
• Garcia, Alfredo Sanchez & Strandberg, Rune (2019). Analytical Expressions for Radiative Losses in Solar Cells. Full text in Research Archive
• Søndergaard, Sissel Tind; Odden, Jan Ove & Strandberg, Rune (2018). Temperature dependent suns-Voc of mc-Si cells from different ingot positions. Full text in Research Archive
• Strandberg, Rune (2017). The JV-characteristics of high-efficiency PV-concepts. Full text in Research Archive
• Søndergaard, Sissel Tind; Strandberg, Rune & Odden, Jan Ove (2017). Minority Carrier Lifetime Variations in Multicrystalline Silicon Wafers with Temperature and Ingot Position. Full text in Research Archive
• Strandberg, Rune (2017). Fotoner - hvordan høste dem mest mulig effektivt? Full text in Research Archive
• Strandberg, Rune (2017). Analytic JV-Characteristics of Ideal Impurity PV-Cells. Full text in Research Archive
• Strandberg, Rune (2016). Solceller. Full text in Research Archive
• Strandberg, Rune (2016). Comparison of the Sensitivity to Spectral Variation of Voltage- and Current-Matched Tandem Devices with Luminescent Coupling and Thickness Optimization. Full text in Research Archive
• 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. Full text in Research Archive
• Berthod, Charly; Strandberg, Rune; Odden, Jan Ove & Sætre, Tor Oskar (2016). Reduced Temperature Sensitivity of Multicrystalline Silicon Solar Cells with Low Ingot Resistivity. Full text in Research Archive
• Strandberg, Rune (2015). Emitterende energihøstere. Full text in Research Archive
• Strandberg, Rune (2015). Spectral and Temperature Sensitivity of Area De-Coupled Tandem Modules. Full text in Research Archive
• Strandberg, Rune (2015). Measurement of minority carrier lifetime at elevated temperature. Full text in Research Archive Show summary

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

• Skomedal, Gunstein & Strandberg, Rune (2015). Framtida møtes best forlengs. Fædrelandsvennen. ISSN 0805-3790. 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. Full text in Research Archive
• Strandberg, Rune (2015). Arealdekoblede tandemmoduler. Full text in Research Archive
• Strandberg, Rune (2015). Solcellekonsepter med høy virkningsgrad. 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. Full text in Research Archive
• Strandberg, Rune (2015). Area de-coupled tandem modules. Full text in Research Archive
• Strandberg, Rune (2014). Fornybar energi. Full text in Research Archive
• Strandberg, Rune (2013). Production data from 45 kWp solar power plant in Kristiansand. Full text in Research Archive
• Eikeland, Torgeir; Imenes, Anne Gerd & Strandberg, Rune (2010). Solcelleparker kan erstatte vannkraft. [Journal]. Fedrelandsvennen. Full text in Research Archive Show summary

  Kommentar: Tittelen er feilsitert.

• Strandberg, Rune & Reenaas, Turid Worren (2009). Photofilling of Intermediate Bands. Full text in Research Archive
• Strandberg, Rune & Reenaas, Turid Worren (2008). Modelling of the Electron Concentration in an Intermediate Band. Full text in Research Archive
• Strandberg, Rune & Reenaas, Turid Worren (2008). Investigation of an alternative intermediate band solar cell design. Full text in Research Archive
• Strandberg, Rune (2008). Intermediate Band Solar Cells. Full text in Research Archive
• 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. Full text in Research Archive
• Strandberg, Rune; Thomassen, Sedsel Fretheim & Worren, Turid (2006). Quantum dot intermediate band solar cells. Full text in Research Archive
• Strandberg, Rune & Worren, Turid (2006). PC1D-simulations of solar cells containing regions with enhanced infrared absorption. Full text in Research Archive
• Thomassen, Sedsel Fretheim; Worren, Turid; Fimland, Bjørn-Ove; Strandberg, Rune & Myrvågnes, Geir (2006). Quantum Dot Intermediate Band Solar Cells. Full text in Research Archive
• Garcia, Alfredo Sanchez & Strandberg, Rune (2022). Theoretical Studies in Solar Cell Physics. Universitetet i Agder. ISSN 9788284271033. Full text in Research Archive Show summary

  In this thesis, we develop analytical models with the purpose of expanding knowledge and gaining understanding of some of the internal mechanisms that limit the efficiency of single-junction solar cells. We focus on three distinct topics: fundamental energy losses, the temperature sensitivity of single-junction solar cells and the effect of the series resistance on the maximum power point. The thesis is divided in two parts. The first part reviews basic solar cell physics topics and introduces some more advanced concepts to provide the reader with the necessary background to understand the attached papers. The latter constitute the second part of the thesis.

• Skaaland, Åsbjørn; Ricke, Michael; Wallevik, Kristin; Strandberg, Rune & Imenes, Anne Gerd (2011). Potential and Challenges for Building Integrated Photovoltaics in the Agder Region. NORCE Research AS. Full text in Research Archive

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