Persons at STU
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|Language of final thesis:||English|
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|Title of the thesis:||Role of Defects in Organic Semiconductors for Solar Cells|
|Summary:||The main problem of organic solar cell application is their low stability and lifetime. Different degradation agents induce the generation of electrically active defects in organic semiconductors, which results in the deterioration of electrical properties of organic solar cells. These defects may behave as the charge traps and significantly affect the charge transport. The knowledge of the origin of defects and the possibilities of their elimination is therefore an important demand for the development of organic electronics.
The aim of this dissertation was to find out the influence of different degradation agents on the defect state generation in the P3HT:PCBM solar cell and the impact of these agents on solar cell performance. The role of the defect states was studied on solar cell samples exposed to various degradation agents: oxygen, water, ozone, solar radiation as well as the intrinsic influences. New knowledge was obtained by the combination of standard experimental techniques suitable for electrical, optical, and structural thin film characterization with transient techniques based on the charge measurement. The defect states were measured with charge deep-level transient spectroscopy.
Our results suggest that above-mentioned degradation agents trigger three types of dominant degradation processes. The first is the generation of defect states in the active layer, which was common for all external degradation agents. The second is the degradation of the cathode-organic interface which was mostly determined by humidity. The third process can be ascribed to the morphological changes of the active layer which were dominant for the degradation of encapsulated cells.|
|Key words:||organic solar cell, defect states, deep-level transient spectroscopy, degradation|
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