Plasmonic silver nanoparticles for improved organic solar cells

AbsractIn the present work we compare the performance of organic solar cells, based on the bulk heterojunction system of P3HT:PCBM when adequate silver nanoparticles (NPs) are incorporated in two distinct places among the device structure. Introduction of NPs on top of the transparent anode revealed better overall performance with an increased efficiency of 17%. Alternatively, placing the NPs on top of the active photovoltaic layer resulted to 25% higher photo-current generation albeit with inferior electrical characteristics (i.e series and shunt resistance). Our findings suggest that enhanced scattering to non-specular directions from NPs site is maximized when penetrating light meets the particles after the polymer blend, but even this mechanism is not sufficient enough to explain the enhanced short circuit current observed. A second mechanism should be feasible; that is plasmon enhancement which is more efficient in the case where NPs are in direct contact with the polymer blend. J–V characteristics measured in the dark showed that NPs placed on top of the ITO film act as enhanced hole conducting sites, as evident by the lower series resistance values in these cells, suggesting this mechanism as more significant in this case.

► SE revealed that PCBM concentrates in the vicinity of the Ag NPs when in contact with the active layer.
► Ag NPs placed on top of the active layer enhance the non-specular reflectivity.
► Ag NPs embedded in the PEDOT:PSS layer transfer holes more efficiently leading to lower Rs values.
► Enhanced absorption and scattering of light occurs when Ag NPs are placed on top of the active layer.