Research On The Surface Plasmon-enhanced Organic Bulk Heterojunction Solar Cell

Polymer bulk heterojunction solar cells are a promising alternative to traditional inorganic solar cells due to their potential as a low-cost source of renewable energy. However, organic solar cells design and optimization is complicated because the light absorption depth is ~10×larger than the electron diffusion length in most organic polymers, which often forces a trade off between light absorption and exciton harvesting efficiency.The main objective of this thesis is to study the surface plasmon enhanced optical absorption and photocurrent in organic bulk heterojunction photovoltaic devices using Ag nanoparticles. And the main achievements obtained are summarized as follows:Firstly, we reported synthesized Ag nanoparticles with diameter of 7 nm on average by the chemical method. By incorporating plasmonic AgNPs with lower density and high density between the PEDOT:PSS buffer layer and the active layer with the structure of ITO /PEDOT:PSS /AgNPs layer/ P3HT:PCBM/LiF/Al, the power conversion efficiency of the polymer solar cells was increased from 2.89% to 3.21% and 3.38%, increased by 11.07% and 16.96%, respectively. The introduction of AgNPs layer effectively improves the optical absorption of the active layer owing to the increased plasmonic near field couple to the active layer. The incident photon to current efficiency (IPCE) measurement demonstrates that the IPCE peak value increases from 48% to 54% around the wavelength of 500 nm for the cell integrating a high density of AgNPs.Secondly, ultrathin silver nanoislands were fabricated by vaccum evaporation deposition on indium tin oxide electrodes. Plasmon-active silver nanoparticle layers were incluced in polymer bulk heterojunction solar cells with the structure of ITO /PEDOT:PSS /AgNPs layer/ P3HT:PCBM/LiF/Al. The introduction of such particles films lead to enhanced optical absorption efficiency and the corresponding enhanced photovoltaic conversion efficiency. The power conversion efficiency of the polymer solar cells was increased from 2.84% to 3.64%, increased by 28%. It's shown that plasmonic near field can couple to the active layer across the buffer layer.Thirdly, we further investigated the influence of film thickness of the PEDOT:PSS buffer layer on the performance of the surface plasmon enhanced polymer solar cells. With the decrease of the film thickness of the PEDOT:PSS layer, the optical absorption efficiency was increased and photoconversion increased consequently.The results indicate that the effect of plasmonic can be manipulated by varying the distance of the metal particles from the active layer.