of Technology (MIT), Cambridge, MA (United States)
#C60 refractive index database trial
In particular, as an experimental trial system, the approach is applied here to a ultra-thin film solar cell with a SubPc/C60 photovoltaic structure. This approach provides a general strategy for optimizing the power conversion efficiency of a wide range of OPV structures. Based on the experimentally obtained complex refractive indices of the OPV materials and the thickness-dependence of the internal quantum efficiency of the OPV active layer, we analyze the potential benefits of light trapping strategies for maximizing the overall power conversion efficiency of the cell.
Finally, reproducibility, angstrom-level sensitivity, and simplicity of the method are highlighted showcasing its applicability for studying electronic coupling between any vapor-deposited material systems where real-time measurements during thin film growth are possible.We describe a general method for maximizing the short-circuit current in thin planar organic photovoltaic (OPV) heterojunction cells by simultaneous optimization of light absorption and carrier collection. Translation of such interactions in terms of dielectric constants reveals plasmonic type resonance absorptions resulting from oscillations of the excited state wave functions between the two materials across the interface. Applying the same methodology for C60 deposited on phthalocyanine thin films, the analyses shows strong, anomalous features-in comparison to C60 deposited on Si O 2-of the electronic wave functions corresponding to specific excitation energies in C60 and phthalocyanines. The analysis, which does not require any model fitting, reveals direct observations of electronic coupling between frontier orbitals under optical excitations leading to delocalization of the corresponding electronic wave functions with thickness or, equivalently, number of molecules away from the interface in C60 and MeO-TPD deposited on an insulating substrate ( Si O 2 ).
Here, we introduce an in situ spectroscopic ellipsometry data analysis method called differential analysis in real time (DART) with the ability to directly probe electronic coupling due to intermolecular interactions along the thickness direction using vacuum-deposited organic semiconductor thin films as a model system. In these devices, charge transport and interfaces between multiple layers occur along the thickness or vertical direction, and thus such electronic interactions between different molecules-same or different-are crucial in determining the device properties. These interactions dictate electronic and optical processes at interfaces, and is especially relevant in the case of thin film optoelectronic devices such as organic solar cells. The electronic wave functions of an atom or molecule are affected by its interactions with its environment.
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