Reducing toxicity and enhancing broadband solar energy harvesting of ultra-thin perovskite solar cell via SiO₂ nanophotonic structure

Perovskite solar cell had the advantages of low cost, high efficiency and flexibility, which had significant development potential. Reducing the thickness of the perovskite absorber layer was a practicable method to reduce the content of toxic lead elements, however, an insufficient light absorption and low photocurrent were usually observed due to the shorten optical path length. In this study, SiO₂ nanophotonic structure was introduced and designed by electromagnetic theory to allow the perovskite absorber layer to become thinner, while did not decrease its light absorption and photocurrent. The geometrical parameters of SiO₂ nanophotonic structure was optimized by finite-difference time-domain (FDTD) method combined with particle swarm optimization algorithm to obtain the largest light absorption enhancement. When SiO₂ nanophotonic structure was used, the perovskite solar cell with a 200 nm thickness perovskite absorber layer can generate the same photocurrent as the planar perovskite solar cell with a 300 nm thickness perovskite absorber layer, which can reduce toxic lead elements of perovskite material as high as 33%. The feasibility of applying SiO₂ nanophotonic structure to different perovskite solar cells was further investigated.