基于光学黑洞的单纳米线太阳电池研究

Study of single-nanowire solar cells based on optical black hole

为实现对太阳光的宽波段高效吸收,引入光学黑洞(optical black hole,OBH)概念,用有限元方法对单纳米线太阳电池(SNSCs)进行电磁仿真和结构设计。剖析了极化模式、OBH尺寸、核壳匹配、折射率阶梯分层等因素对OBH SNSCs的陷光和光学吸收性能的影响。研究表明:较以往介电常数匹配方式,利用折射率匹配设计可进一步提高OBH系统的光学吸收性能;借助微纳结构对光波的调控,可实现全向宽带高效吸收,从而将OBH应用于微纳光伏系统;进一步发现,可通过优化内核半径和外壳折射率分布来提高基于OBH的非晶硅(a-Si:H)SNSCs吸收效率,获得的光电流较传统无包层a-Si:H SNSCs提升约300%。

To realize the broadband and efficient absorption to the sunlight, the single nanowire solar cells （SNSCs） based on the optical black hole （OBH） were electromagnetically simulated and designed using the finite-element method. The influences of the incident polarization, the size of OBH, the material matching condition of the core and shell, the stepping refractive-index profile, etc, on the light trapping and absorption efficiency of OBH SNSCs were investigated thoroughly. Results show that the absorp- tion performance of the OBH system can be further improved by using the matching design based on the refractive index, rather than the permittivity matching. Through light absorption regulating by the miero/nano-structures, an omnidirectional and wide- band absorption can be achieved, showing a high suitability for micro/nano photovoltaic systems. Further study indicates that the light absorption of the hydrogenated amorphous silicon （a-Si： H） SNSCs can be obtained by optimally designing the core radius and the refractive index distribution of the OBH shell. The photocurrent can be enhanced up almost 300% compared to bare a-Si： H SNSCs. Keywords： optical black hole （OBH）; single nanowire solar cells; refractive index matching; omnidirectional broadband optical absorption