Le Khai Q, John Sajeev
Opt Express. 2014 Jan 13;22 Suppl 1:A1-12. doi: 10.1364/OE.22.0000A1.
We demonstrate, numerically, that with a 60 nanometer layer of optical up-conversion material, embedded with plasmonic core-shell nano-rings and placed below a sub-micron silicon conical-pore photonic crystal it is possible to absorb sunlight well above the Lambertian limit in the 300-1100 nm range. With as little as 500 nm, equivalent bulk thickness of silicon, the maximum achievable photo-current density (MAPD) is about 36 mA/cm2, using above-bandgap sunlight. This MAPD increases to about 38 mA/cm2 for one micron of silicon. Our architecture also provides solar intensity enhancement by a factor of at least 1400 at the sub-bandgap wavelength of 1500 nm, due to plasmonic and photonic crystal resonances, enabling a further boost of photo-current density from up-conversion of sub-bandgap sunlight. With an external solar concentrator, providing 100 suns, light intensities sufficient for significant nonlinear up-conversion can be realized. Two-photon absorption of sub-bandgap sunlight is further enhanced by the large electromagnetic density of states in the photonic crystal at the re-emission wavelength near 750 nm. It is suggested that this synergy of plasmonic and photonic crystal resonances can lead to unprecedented power conversion efficiency in ultra-thin-film silicon solar cells.
我们通过数值模拟证明，在亚微米硅锥形孔光子晶体下方嵌入等离子体核壳纳米环，并放置一层60纳米厚的光学上转换材料，能够在300 - 1100纳米范围内吸收远高于朗伯极限的太阳光。仅用500纳米等效体厚度的硅，利用高于带隙的太阳光，可实现的最大光电流密度（MAPD）约为36 mA/cm²。对于1微米厚的硅，该MAPD增加到约38 mA/cm²。由于等离子体和光子晶体共振，我们的结构在1500纳米的子带隙波长处还能将太阳强度增强至少1400倍，从而通过子带隙太阳光的上转换进一步提高光电流密度。使用提供100倍太阳光的外部太阳能聚光器，可以实现足以进行显著非线性上转换的光强。在接近750纳米的再发射波长处，光子晶体中的大电磁态密度进一步增强了子带隙太阳光的双光子吸收。有人认为，等离子体和光子晶体共振的这种协同作用可在超薄硅太阳能电池中实现前所未有的功率转换效率。
