Modeling spectral matching in two- and four-terminal thin-film silicon tandem solar cells

Steve Reynolds, Vladimir Smirnov, Kaining Ding

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    Tandem thin-film silicon solar cells offer the prospect of improved spectral matching, and hence increased solar conversion efficiencies, over comparable single cells. The deposition process naturally results in the constituent sub-cells being connected electrically as well as optically in series, with each therefore constrained to operate at the same load current. By careful
    adjustment of absorber layer thicknesses, conversion efficiency may be optimised under this constraint for a given spectral distribution, typically the AM1.5G spectrum. However, variations in spectral quality arising from seasonal and diurnal effects alter the proportion of photogenerated current from each cell, causing imbalance and consequent reductions in efficiency. Here we compare the series-connected two-terminal tandem cell with a four-terminal
    tandem cell, in which both cells remain optically in series but each may be operated independently at its maximum power point appropriate to the conditions of service. A semiempirical model is used, where realistic variations in average photon energy between 1.8 and 2.0 eV are introduced by a wavelength-dependent linear scaling factor applied to the AM1.5G spectrum. A two-terminal tandem cell optimised for AM1.5G operation reaches a peak efficiency of 11.2%, falling to 9.6% and 10.3% respectively at the spectral extremes. For the same subcell parameters, the model predicts a progressive increase in four-terminal conversion efficiency, from 10.6% to 11.7% over the same range. We also compare tandem-cell with single-cell performance, and discuss the practical difficulties of developing a four-terminal tandem module.
    Original languageEnglish
    Title of host publicationECOS 2011 - 24th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Novi Sad, Serbia (4-7 July 2011)
    Pages3346-3357
    Number of pages12
    Publication statusPublished - 5 Jul 2011
    Event24th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems - Novi Sad, Serbia
    Duration: 4 Jul 20117 Jul 2011
    http://epoc.mec.upt.ro/conferinte/ECOS.pdf

    Conference

    Conference24th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems
    CountrySerbia
    CityNovi Sad
    Period4/07/117/07/11
    Internet address

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    Cite this

    Reynolds, S., Smirnov, V., & Ding, K. (2011). Modeling spectral matching in two- and four-terminal thin-film silicon tandem solar cells. In ECOS 2011 - 24th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Novi Sad, Serbia (4-7 July 2011) (pp. 3346-3357)