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A molecular spin-photovoltaic device

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Science  18 Aug 2017:
Vol. 357, Issue 6352, pp. 677-680
DOI: 10.1126/science.aan5348
  • Fig. 1 Schematic of the device, together with its magnetocurrent and photovoltaic characterization.

    (A) Schematic representation of the C60-based molecular spin-photovoltaic (MSP) device, composed (from bottom to top) of Si, SiO2, Co, AlOx, C60, and Ni80Fe20. B, magnetic field; hv, photon energy. (B) Magnetocurrent (MC) on the MSP device measured at 295 and 80 K with a bias of 10 mV in dark conditions. The MC is defined as the relative change in electrical current [MC (in percent) = (IPIAP)/IAP × 100, where IP and IAP represent the current for parallel and antiparallel orientations of the magnetization of the Co and Ni80Fe20 electrodes, respectively] as a function of magnetic field. The arrows in the image indicate the orientations of the magnetization. (C) Current-voltage curves measured with and without white-light irradiation (7.5 mW/cm2) at room temperature when the relative orientation of the electrodes was parallel (Iout, output current; Vapp, applied voltage). The open-circuit voltage (VOC) and the short-circuit current (ISC) are indicated on the curve. In the measurement setup, the Co electrode is grounded.

  • Fig. 2 Device functioning principle, together with its photovoltaic characterization in a magnetic field.

    (A) The MSP device operating as a short-circuited single-layer molecular solar cell without (diagram 1) and with (diagram 2) light irradiation. h+, hole; e, electron. (B) Current versus magnetic field measurement with and without light irradiation at 80 K (short-circuit mode), corresponding to the diagrams in (A). The photogenerated current is not sensitive to the magnetic field. (C) A MSP device operating in open-circuit mode under the application of a magnetic field, in the parallel (diagram 1) and antiparallel (diagram 2) configurations. (D) Applied voltage versus magnetic field measurement at 80 K in the parallel and antiparallel configurations (equal to VOC because we operated in open-circuit mode), corresponding to the diagrams in (C). VOC increased when the magnetic moments of the ferromagnetic (FM) electrodes became antiparallel. (E) I-V curves measured under white-light irradiation (7.5 mW/cm2) for the cases in which the magnetic moments of the FM electrodes were parallel and antiparallel. The changes in VOC and Iout are indicated on the curves. The measurements shown were performed at 80 K.

  • Fig. 3 Operation of the device at a constant applied voltage bias under different light irradiation conditions.

    (A) Manipulation of I-B curves in a MSP device by the irradiated light intensity under a constant bias of 10 mV at 80 K. (B) In the particular case of IP = –IAP, the flow direction of the current can be freely inverted by the magnetic field controlling the orientation of the magnetic electrodes, without changes in its absolute value. (C) Output current Iout (IAP and IP) and normalized magnetocurrent response versus the irradiated light intensity; the curves were calculated from discrete data measured as shown in (A).

  • Fig. 4 Operation of the device at a constant light irradiation condition under different applied voltage biases, together with the more complex electro-optical modulation with varying voltage and light.

    (A) Manipulation of I-B curves in a MSP device under different applied biases and constant light irradiation of 7.5 mW/cm2 at 80 K. (B) Change in current (ΔI) under the application of a magnetic field, obtained as a function of both applied light irradiation and applied voltage bias. (C) Electro-optical modulation, varying both the applied voltage bias and the light irradiation. The input values are selected in such a way that Vapp exactly cancels VOC,P. The device output is a spin photogenerated current.

Supplementary Materials

  • A molecular spin-photovoltaic device

    Xiangnan Sun, SauÌ^l Vélez, Ainhoa Atxabal, Amilcar Bedoya-Pinto, Subir Parui, Xiangwei Zhu, Roger Llopis, Fèlix Casanova, Luis E. Hueso

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S4
    • References

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