为提高有机-无机杂化钙钛矿太阳能电池(PSCs)光吸收效率、平衡有源层中载流子产生速率, 将周期性纳米光栅结构引入到PSCs器件结构中。分析了光栅周期、光栅高度和有源层厚度对表面等离子激元(SPPs)与法布里-珀罗(F-P)共振耦合模式的影响。通过改变光栅周期, 实现了SPPs与F-P共振耦合波长范围与钙钛矿材料的弱吸收光谱区域相重合, 同时光栅高度的增加可以增大耦合模式的光谱宽度。SPPs与F-P共振耦合模式实现了金属电极与电子传输层(ETL)界面处的局域电场增强。结果表明: 场增强效应扩展到有源区, 有效提高了PSCs有源层远入射光侧在570~800 nm波长范围内的光吸收, 进而提高了有源层远入射光区域的载流子产生速率。当光栅周期为250 nm、光栅高度为50 nm、源层厚度为300 nm时, PSCs在太阳光弱吸收光谱区域内的本征吸收提高了~12%, 有源层远入射光侧载流子产生速率提高了~41%。

Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently, methylammonium lead halide perovskites were identified as promising absorbers for solar cells. To improve the absorption of perovskite solar cells(PSCs) and modify the distribution of the generation rate of charge carriers, the one dimensional periodic sinusoidal nano-grating structure is introduced into PSCs. We characterize the coupled modes between surface plasmon polaritons(SPPs) and Fabry-Pérot(F-P) resonance, and analyze how they are affected by the period and height of the grating and the thickness of the active layer. The coupled modes enhance the light field in the weak absorbance spectrum region. Meanwhile, the width of coupled spectrum shows strong grating height dependence and will get a broad spectrum enhancement when the grating height is larger than 50 nm. The enhanced localized electric field near the interface of Ag/ETL expands into the active layer with an exponential decay length of ~100 nm, results an absorption enhancement near the ETL/active layer interface. We calculate the absorption of the active layer by using a finite-difference time-domain(FDTD) method and the absorbance (the optimized grating structure with the grating period, the grating height and the thickness of active layer is 250 nm, 50 nm and 300 nm, respectively) is improved by 12% in wavelength range of 650-800 nm in transverse magnetic (TM) light incidence condition. We also demonstrate an increased generation rate of charge carriers near the ETL/active layer interface due to the enhanced field. The normalized generation rate increases by 41%(110%) in the position of 250 nm(200 nm) away from the HTL/active layer interface in PSCs. A balanced generation rate in the whole active layer will improve the diffusion of electrons and the collection of carriers, result in the increasement of the power conversion efficiency.