The role of colloidal plasmonic nanostructures in organic solar cells
C. R. Singh, T. Honold, T. P. Gujar, M. Retsch, A. Fery, M. Karg, M. Thelakkat:
PCCP, 18, 23155-23163 (2016)
Plasmonic particles can contribute via multiple processes to the light absorption process in solar cells. These particles are commonly introduced into organic solar cells via deposition techniques such as spin-coating or dip-coating. However, such techniques are inherently challenging to achieve homogenous surface coatings as they lack control of inter-particle spacing and particle density on larger areas. Here we introduce the interface assisted colloidal self-assembly as a concept for the fabrication of well-defined macroscopic 2-dimensional monolayers of hydrogel encapsulated plasmonic gold nanoparticles. The monolayers showed a pronounced extinction in the visible wavelength range due to the localized surface plasmon resonance with excellent optical homogenity. Moreover this strategy allowed for the investigation of the potential of plasmonic monolayers at different interfaces of P3HT:PCBM based inverted organic solar cell. In general, for monolayers located anywhere underneath the active layer, the solar cell performance decreased due to the parasitic absorption. However with thick active layers, where the low hole mobility limited the charge transport to the top electrode, the plasmonic monolayer near to that electrode spatially redistributed the light and charge generation close to the electrode led to an improved performance. This work systematically highlights trade-offs that need to be critically considered for designing an efficient plasmonically enhanced organic solar cell.