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978-3-8439-2074-2, Reihe Physik
Photoexcitation and energy transfer processes in composite systems of dyes and microcrystalline silicon
127 Seiten, Dissertation Carl von Ossietzky Universität Oldenburg (2014), Hardcover, A5
The suitability of composite materials consisting of dye molecules in a microcrystalline silicon matrix (µc-Si:H matrix) for photovoltaic applications is examined by numerical simulations and by various spectroscopic techniques, such as , transmission-/reflection-/absorption-spectroscopy and temperature-dependent photoluminescence.
Numerical simulations under standard test conditions of hybrid dye/µc-Si:H pin structures result in a potential increase of efficiency by more than 30% compared to a (conventional) µc-Si:H cell. Thus yielding for the same device efficiency, the thickness of the composite system can be potentially reduced by almost two thirds.
For the interpretation of temperature-dependent µc-Si:H photoluminescence spectra Planck's generalized law is extended to describe the radiative recombination via band tail states. This substantial refinement of existing approaches allows for the modeling of temperature-dependent spectra over the entire measured temperature range and furthermore provides access to the chemical potential of electron-hole ensemble, which also is the upper limit of the open circuit voltage attainable in a processed solar cell, and furthermore yields quantitative information on band tail energies.
The optical constants of the novel dye PA-PTCDI are determined by transmission-/reflection-/absorption-spectroscopy, both, in solution and as (deposited) thin films. Absorption measurements on PA-PTCDI/µc-Si:H composites show that PA-PTCDI survives the processing conditions of µc-Si:H. The detailed analysis of photoluminescence spectra at T = 20 K within the framework of the extended method developed in this thesis moreover reveals that the chemical potential of the PA-PTCDI/µc-Si H hybrid system is significantly larger compared to the bare µc-Si:H layer, which indicates the presence of a transfer of the photoexcited state from the PA-PTCDI to the adjacent µc-Si:H matrix.