Potential of plasmonic nanofibrous active layers
The paper 'Nanostructure and photovoltaic potential of plasmonic nanofibrous active layers' has been chosen as the Editor's Choice in the Wiley journal 'Small'.
The authors* explain how the nanofibrous active layers offer hierarchical control over molecular structure, and the size and distribution of electron donor/acceptor domains, beyond conventional organic photovoltaic architectures. This structure is created by forming donor pathways via electrospinning nanofibres of semiconducting polymer, then infiltrating with an electron acceptor.
Electrospinning induces chain and crystallite alignment, resulting in enhanced light-harvesting and charge transport. In this study, the charge transport capabilities were predicted, and the charge separation and dynamics were evaluated in the active layers, to assess their photovoltaic potential.
Through X-ray and electron diffraction, the fibre nanostructure was elucidated, with uniaxial elongation of the electrospinning jet aligning the polymer backbones within crystallites orthogonal to the fibre axis, and amorphous chains parallel. The authors explain that this structure forms when anisotropic crystallites, pre-assembled in solution, become orientated along the fibre - this is a configuration with high charge transport potential.
The authors recorded competitive dissociation of excitons which formed in the photoactive nanofibres, with 95%+ photoluminescence quenching upon electron acceptor introduction. Transient absorption studies have revealed that adding silver nanoparticles to the fibres improves charge generation and/or lifetimes.
1 ns post-excitation, the plasmonic architecture contained 45% more polarons, per exciton formed, than the bulk heterojunction. Enhanced exciton populations, therefore, may be successfully translated into additional charge carriers.
*Led by this department, in collaboration with the Department of Physics (Oxford), the University of Warwick and the Electron Physical Science Centre at Diamond Light Source.
