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978-3-8439-2074-2, Reihe Physik

Sven Burdorf
Photoexcitation and energy transfer processes in composite systems of dyes and microcrystalline silicon

127 Seiten, Dissertation Carl von Ossietzky Universität Oldenburg (2014), Hardcover, A5

Zusammenfassung / Abstract

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.