Ginzton Laboratory, Stanford University, Stanford, CA 94305, USA.
Proc Natl Acad Sci U S A. 2010 Oct 12;107(41):17491-6. doi: 10.1073/pnas.1008296107. Epub 2010 Sep 27.
Establishing the fundamental limit of nanophotonic light-trapping schemes is of paramount importance and is becoming increasingly urgent for current solar cell research. The standard theory of light trapping demonstrated that absorption enhancement in a medium cannot exceed a factor of 4n(2)/sin(2)θ, where n is the refractive index of the active layer, and θ is the angle of the emission cone in the medium surrounding the cell. This theory, however, is not applicable in the nanophotonic regime. Here we develop a statistical temporal coupled-mode theory of light trapping based on a rigorous electromagnetic approach. Our theory reveals that the conventional limit can be substantially surpassed when optical modes exhibit deep-subwavelength-scale field confinement, opening new avenues for highly efficient next-generation solar cells.
确定纳米光子光捕获方案的基本限制对于当前的太阳能电池研究至关重要，而且这种需求变得越来越迫切。光捕获的标准理论表明，介质中的吸收增强不能超过 4n(2)/sin(2)θ 的因子，其中 n 是活性层的折射率，θ 是细胞周围介质中发射锥的角度。然而，该理论在纳米光子学领域并不适用。在这里，我们基于严格的电磁方法开发了一种用于光捕获的统计时间耦合模式理论。我们的理论表明，当光学模式表现出深亚波长尺度的场限制时，传统的限制可以大大超过，为高效的下一代太阳能电池开辟了新途径。
