![]() ![]() The spectral slices are taken at the maximum signal, time 400 ns below 10% and at 500 ns above 10%. ![]() b tr-EPR spectra acquired in the x-orientation as a function of pentacene concentration with the simulated triplet contribution shown in orange. The coloured traces are simulations of the rotation pattern of each molecular axes, calculated for the two inequivalent sites in the crystal lattice, where orange, cyan and teal correspond to x, y and z, respectively. Angles are defined as between the normal to the substrate and the magnetic field direction. a tr-EPR spectra of the 1 µm 0.5% pentacene doped p-terphenyl film at different orientations within the magnetic field taken at time 400 ns. Tr-EPR of ordered pentacene films as a function of orientation and concentration. The error in crystallite size was estimated as the difference between the Lorentzian and Gaussian calculation of the Scherrer equation.⁴⁷d Unit cell of the pentacene showing the parallel dimer (teal) and herringbone dimer (cyan) All films are 1 μm except the 100% pentacene which is 100 nm-XRD intensity is normalised to the thickness. increased lattice spacing) 5 and 100% pentacene are close to instrument resolution and consequently have the largest error in grain size. c Variation in scattering angle and grain size (calculated from the Scherrer equation ³¹) with increasing pentacene concentration, indicating a linear shift to towards lower scattering angles (i.e. The inset shows the contact angle of p-terphenyl (left) and pentacene (right) on the substrate. b Close-up of the (003) peak where (*) corresponds to the pentacene peak position and (†) p-terphenyl position. The dilute samples form large platelets typical of p-terphenyl, whereas an increase in dopant concentration leads to fragmentation into smaller faceted grains. a SEM cross-sections with a 1-μm scale bar. Morphology and structure of the 1-μm-thick pentacene films as a function of concentration. #Tt5tt redirector freeWe find that the ability of quintets to separate into free triplets is promoted in the parallel dimers and this provides molecular design rules to control the triplets, favouring either enhanced photovoltaic efficiency (parallel) or strongly bound pairs that could be exploited for logic applications (herringbone). Using electron paramagnetic resonance spectroscopy, we provide compelling evidence for the formation of distinct quintet excitons in ambient conditions, with intrinsically distinctive electronic and kinetic properties. In this work, we produce highly ordered dilute pentacene films with distinct parallel and herringbone dimers and aggregates. However, the pathways of the coupled triplets into free species, and their dependence on the intermolecular geometry, has not been fully explored. Singlet fission is a particularly appealing mechanism as it generates two excitons from a single photon. Building efficient triplet-harvesting layers for photovoltaic applications requires a deep understanding of the microscopic properties of the components involved and their dynamics. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |