Study on photonic-crystal effects on photovoltaic materials towards efficient photovoltaic devices

我们展示了利用二维光子晶体的超薄（50 nm）硅有源层光探测器件的光吸收和光电转换效率的增强。我们通过实验和模拟表明，光子带边缘的光共振效应增强了有源层内的入射光吸收。我们还发现，由于光子带边模式与本征材料吸收之间的q因子匹配更好，具有更深空穴的光子晶体可以导致更大的吸收增强。实验观察到的光子晶体样品在光子带边波长处的光电流相对于没有光子晶体的对照样品增加了约20倍，这归因于改进的Q匹配。我们还研究了利用光子晶体增强薄硅光伏器件的宽带光吸收。

We demonstrate an enhancement of the optical absorption and photoelectric-conversion efficiency of an ultrathin (50 nm) silicon active-layer photodetecting device using a two-dimensional photonic crystal. We show both experimentally and with simulations that the incident-light absorption within the active layer is enhanced by optical-resonance effects at the photonic band edge. We also find that a photonic crystal with deeper holes can lead to an even larger absorption enhancement due to better Q-factor matching between the photonic band-edge modes and the intrinsic material absorption. The experimentally observed photocurrent of the fabricated photonic crystal sample is increased by a factor of around 20 at the photonic band-edge wavelength relative to that of a control sample without the photonic crystal which is attributed to the improved Q matching. We also investigate broadband optical absorption enhancement in thin silicon photovoltaic devices by photonic crystal.