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首页> 外文期刊>Physical review. B, Condensed Matter And Materals Physics >Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics
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Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics

机译：II型GaSb / GaAs量子点光伏电池的中带吸收特性分析

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摘要

Quantum-dot (QD) intermediate-band (IB) materials are regarded as promising candidates for high-efficiency photovoltaics. The sequential two-step two-photon absorption processes that take place in these materials have been proposed to develop high-efficiency solar cells and infrared (IR) photodetectors. In this work, we experimentally and theoretically study the interrelation of the absorptivity with transitions of carriers to and from the IB in type-II GaSb/GaAs QD devices. Our devices exhibit three optical band gaps with: E_L = 0.49 eV, E_H = 1.02 eV, and E_G = 1.52 eV, with the IB located 0.49 eV above the valence band. These values are well supported by semiempirical calculations of the QDs electronic structure. Through intensity-dependent two-photon photocurrent experiments, we are able to vary the filling state of the IB, thus modifying the absorptivity of the transitions to and from this band. By filling the IB with holes via E = 1.32eV or E = 1.93 eV monochromatic illumination, we demonstrate an increase in the E_L-related absorptivity of more than two orders of magnitude and a decrease in the En-related absorptivity of one order of magnitude. The antisymmetrical evolution of those absorptivities is quantitatively explained by a photoinduced shift of the quasi-Fermi level of the IB. Furthermore, we report the observation of a two-photon photovoltage, i.e., the contribution of subband gap two-photon absorption to increase the open-circuit voltage of solar cells. We find that the generation of the two-photon photovoltage is related, in general, to the production of a two-photon photocurrent. However, while photons with energy close to E_L participate in the production of the two-photon photocurrent, they are not effective in the production of a two-photon photovoltage. We also report the responsivity of GaSb/GaAs QD devices performing as optically triggered photodetectors. These devices exhibit an amplification factor of almost 400 in the IR spectral region. This high value is achieved by minimizing—via doping—the absorptivity in the IR range of the QDs under equilibrium conditions.
机译：量子点（QD）中带（IB）材料被视为高效光伏的有前途的候选材料。已经提出了在这些材料中进行的连续两步两光子吸收过程，以开发高效的太阳能电池和红外（IR）光电探测器。在这项工作中，我们在实验和理论上研究了II型GaSb / GaAs QD器件中载流子与IB之间的迁移与吸收率的相互关系。我们的器件表现出三个光学带隙：E_L = 0.49 eV，E_H = 1.02 eV和E_G = 1.52 eV，IB位于价带上方0.49 eV。 QDs电子结构的半经验计算很好地支持了这些值。通过强度相关的双光子光电流实验，我们能够改变IB的填充状态，从而改变了该波段往返的吸收率。通过通过E = 1.32eV或E = 1.93 eV单色照明向IB填充孔，我们证明了E_L相关的吸收率增加了两个数量级以上，而En相关的吸收率则下降了一个数量级。 。吸收率的反对称演化可以通过光诱导IB准费米能级的迁移来定量解释。此外，我们报告了对双光子光电压的观察，即子带隙双光子吸收对增加太阳能电池开路电压的贡献。我们发现，一般来说，双光子光电压的产生与双光子光电流的产生有关。但是，虽然能量接近E_L的光子参与了双光子光电流的产生，但它们在产生双光子光电压方面却没有作用。我们还报告了用作光触发光电探测器的GaSb / GaAs QD设备的响应度。这些设备在红外光谱区域显示出近400的放大系数。通过在平衡条件下最小化（通过掺杂）QD的IR范围内的吸收率来实现这一高价值。

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  • 来源
    《Physical review. B, Condensed Matter And Materals Physics》 |2017年第12期|125422.1-125422.13|共13页
  • 作者

    I. Ramiro; J. Villa; C. Tablero; E. Antolin; A. Luque; A. Marti; J. Hwang; J. Phillips; A. J. Martin; J. Millunchick;

  • 作者单位

    Instituto de Energia Solar, Universidad Politecnica de Madrid, 28040 Madrid, Spain;

    Instituto de Energia Solar, Universidad Politecnica de Madrid, 28040 Madrid, Spain;

    Instituto de Energia Solar, Universidad Politecnica de Madrid, 28040 Madrid, Spain;

    Instituto de Energia Solar, Universidad Politecnica de Madrid, 28040 Madrid, Spain;

    Instituto de Energia Solar, Universidad Politecnica de Madrid, 28040 Madrid, Spain;

    Instituto de Energia Solar, Universidad Politecnica de Madrid, 28040 Madrid, Spain;

    Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA;

    Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA;

    Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA;

    Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA;

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