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  • SUPPLEMENTARY INFORMATION ARTICLE NUMBER: 16157 | DOI: 10.1038/NENERGY.2016.157

    NATURE ENERGY | www.nature.com/natureenergy 1

    1

    Supplementary Information Low-loss, large-area luminescent solar concentrators fabricated by doctor- blade deposition of quantum dots onto standard window glass Hongbo Li, Kaifeng Wu, Jaehoon Lim, Hyung-Jun Song, and Victor I. Klimov* Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

    Supplementary Figure 1. (a) A histogram of quantum dot (QD) sizes for a sample of thick- shell CdSe/Cd1-xZnxS “giant” QDs (g-QDs) with x = 0.5 and the CdSe mean core diameter of 4 nm (the same sample as in Figure 1 of the article). The average g-QD size is 12.2 ± 2.2 nm. (b) The histogram of particle sizes for the same sample after overcoating g-QDs with silica shells. The average size of a composite particle is 22.5 ± 2.3 nm. The corresponding average silica shell thickness is 5 nm.

    Doctor-blade deposition of quantum dots onto standard window glass for low-loss large-area luminescent solar concentrators

    http://dx.doi.org/10.1038/nenergy.2016.157

  • 2

    Supplementary Figure 2. Photoluminescence (PL) intensities of g-QDs as a function of reaction time during QD overcoating with silica. Normally, it takes 40 hours to complete the shell deposition. The reaction monitored in this plot produces the shell with the average thickness of 5 nm. The first, “time-zero” data point corresponds to a pristine g-QD sample before adding any tetraethyl orthosilicate (TEOS) or ammonium. The data show that there is no any observable PL intensity drop during silica-shell deposition. This is in sharp contrast to previous reports where the deposition of silica shells resulted in at least ~60% of the PL QY drop.

  • 3

    Supplementary Figure 3. (a) PL spectra of uncoated (red; lower panel) and silica-coated (blue; upper panel; 5 nm shell thickness) g-QDs in solutions (dashed) and spin-cast films (solid); in solution samples, uncoated and silica-coated dots are dissolved, respectively, in toluene and ethanol. The ~3 nm redshift of the PL peak of the film vs. solution sample in the case of uncoated g-QDs is a signature of energy transfer (ET). This shift is absent in the case of silica-coated g-QDs indicating a nearly complete suppression of ET. (b) PL QYs of solution vs. film samples. Uncoated g-QDs show a significant PL quenching (by 38%) due to ET upon assembly into close-packed films. On the other hand, the PL QY of silica-coated g- QDs is not modified in films vs. solution samples, which is a direct result of suppressed ET. Error bars represent a standard deviation in PL quantum yields from several independent measurements.

    600 625 650 675 700 725 0.0

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  • 4

    Supplementary Figure 4. A photograph of a setup used to evaluate the performance of fabricated thin-film luminescent solar concentrators (LSCs). It consists of a fiber-coupled light emitting diode (LED) emitting at 405 nm, an integrating sphere, and a compact spectrometer (Ocean Optics). Square-shaped LSCs fabricated on substrates of different sizes (from 1 to 4 inch) with edges masked by a carbon tape.

  • 5

    Supplementary Figure 5. (a) A typical difference spectrum obtained by subtracting the emission spectra collected at the output port of the integrating sphere with and without an LSC. The areas of the "positive" band at ~630 nm and the "negative" band at 405 nm are proportional to, respectively, the total number of the photons emitted by the LSC (SPL) and the number of pump photons absorbed by it (Sabs). The ratio of the two quantities yields the total PL quantum yield of the LSC (ηPL,LSC = SPL/Sabs). (b-e) Measurements of LSCs of different sizes (from 1 to 4 inches; indicated in the figure). The spectra of total, edge, and face emission are shown by black, green, and red colors, respectively. The same spectra are displayed in the inserts in the normalized form. The edge emission spectrum shows a redshift with regard to the spectrum of face emission, which is a result of reabsorption/reemission effects experienced by waveguided light. As expected, this shift increases with increasing the device dimensions.

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    ηPL,LSC = SPL/Sabs

  • 6

    Supplementary Figure 6. Symbols are literature values1-7 of internal quantum efficiencies (ηint) of QD-LSCs in comparison to values realized in the present studies (green circles; device areas from 6.5 to 412 cm2); the data are shown as a function of a light-collecting device area. Green line is ηint calculated using the model described in Supplementary Note 2 for the parameters of LSCs studied in the present work; the model does not account for "extrinsic" losses due to scattering at optical imperfections within the matrix and at the LSC surface. The fact that the experimentally measured internal quantum efficiencies of our LSCs are close to the theoretical curve indicates that these devices are virtually scattering-free; together with reduced losses to re-absorption, this results in the efficiencies that are on a par with or superior to the highest values reported in the literature. In fact, the internal efficiency of our 412 cm2 LSC is comparable to that of a considerably smaller literature device (purple triangle; ~150 cm2 area), which is one of the current record holders.

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  • 7

    Supplementary Table 1. Overview of literature results for QD-based LSCs.1-8 The internal concentration factor is defined as a product of the internal quantum efficiency and the geometric gain factor. Ordered by LSC

    area QD Type QD

    QY LSC Size

    (L× W × T) cm×cm×cm

    Light Source

    Internal Quantum Efficiency

    Internal Concen- tration Factor

    Power Conversion Efficiency

    Notes

    Nano Lett., 2014, 14, 4097-4101.

    Ref 5

    CdSe/CdS core/shell

    86% 2 cm × 2 cm × 0.2 cm

    400 nm 59% 1.5 NA

    Scientific Reports, 2015, 5,

    17777. Ref 4

    CuInS2/ZnS core/shell

    81% 2.2 cm × 2.2 cm

    × 0.3 cm

    450 nm 26.5% 0.5 8.7

    Advanced Energy Materials, 2016,

    6, 1501913. Ref 7

    PbS/CdS core/shell

    40- 50%

    10 cm × 1.5 cm × 0.2 cm

    solar simulator

    4.5% 2.2 NA 1)

    Sol. Energy Mater. Sol. Cells, 2011, 95, 2087-

    2094. Ref 8

    CdSe/CdS/CdZn S/ZnS

    core/multi-shell

    45% 4.95cm × 3.1 cm× 0.4 cm

    solar simulator

    NA NA 2.8% 2)

    ACS Nano, 2014, 8, 3461-3467.

    Ref 2

    Mn 2+

    -doped ZnSe/ZnS

    50% 2.5 cm × 7.5 cm

    × 0.042 cm

    400 nm 37% 8.1 NA

    Optics Express, 2011, 19, 24308-

    24313. Ref 6

    PbS NA 2.54 cm × 7.62 cm× 0.41 cm

    solar simulator

    ~8% 0.2 NA

    Nat Photon, 2014, 8, 392-399.

    Ref 1

    CdSe/CdS core/shell

    45% 21.5 cm × 1.3 cm

    × 0.5 cm

    solar simulator

    10.2% 4.4 NA 3)

    Nat Nano, 2015, 10, 878-885.

    Ref. 3

    CuInSexS2In/ZnS core/shell

    40% 12 cm × 12 cm × 0.3 cm

    solar simulator

    16.7% 1.7 NA

    Present study Silica-coated CdSe/CdZnxS1-x

    core/alloyed shell

    70% 10.2 cm × 10.2 cm

    × 0.16 cm

    405 nm 24% 3.8 NA

    Present study Silica-coated CdSe/CdZnxS1-x

    core/alloyed shell

    70% 20.3 cm × 20.3 cm

    × 0.16 cm

    405 nm 15% 4.8 NA

    1) Three edges of the LSC slab were terminated with mirrors. 2) Three edges of the LSC slab were terminated with mirrors and a diffuse, white reflector was placed at the bottom of the LSC plate. 3) White diffuse reflectors were placed in the proximity to the long-face edges of the LSC.

  • 8

    Supplementary Note 1. Effect of dielectric envir

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